Here is a simplified explanation of why most accomplished photographers use both:

Every adjustment made to an image in Photoshop or any other editing program reduces the end quality . . . except on a RAW file.
Lightroom is designed to make precise adjustments on the RAW file before it is converted to JPG, TIFF, or another kind of file, without having altered the original RAW file or deteriorating the end quality of the file type to which it is converted.
Fine tuning and manipulation of the end file is best done in Photoshop.

MtnMan, I caught your last comment about "when CS6 no longer works (due to Adobe or Microsoft marketing strategies)". It would be my understanding that once any of us would have purchased CS5 or CS6, for example, we own the CD/DVD with the program on it, and it will continue to work (for a very long time) on our own computers. I'm much aware of Microsoft wanting future customers to "rent" OFFICE by making monthly payments for ""Cloud"" access. And Adobe seems well on its way to that marketing model.

Are you suggesting that Adobe will have the future (or current) ability to block us CS5 and CS6 users from continuing to use what is already on our machines?

I will try to explain:
1. I am an avid user of both LR and PS, both are essential to my workflow.
2. the ACR in LR is the same as in PS, it is not a "Lite" version,
3. I do not like Bridge, primarily because I find the interface difficult to see, everything (menus etc. are so small).
4. I use LR as the core to my image management. I now have approx. 106,000 images, any one of which I can find in about 3-20 seconds without knowing the file name (assuming I have the correct external drive plugged in).
5. As soon as my camera is attached to the computer, LR will open and copy those photos into the import module with no intervention from me. I choose a home made import preset to tell LR what to do with those images, ie whether to copy or move, whether to put them into dated folder or altogether into one folder for culling, press the Import button and a couple of minutes later disconnect the camera.
6. Next is to sort into collections, this is the crux of storing files for instant retrieval. Some images go into more than one collection. I rarely use keywords or tags to find images, but I usually do put them onto images in a general way. I do not date the images, the Exif data already contains dates and LR can search on Exif data.
7. All my images are raw files, so when I decide to edit I do that through the built in ACR (which is the same ACR as in PS but with a much better interface)
8. If I need to utilise the facilities offered by PS for further editing, 3 clicks will create a new copy (to preserve the original) open PS and load the image into PS for layering or whatever. PS editing done, just CNT + S and the updated image is back in Lightroom sitting next to the original.
9. No need to save, it's all there in the catalogue and xmp files already.
10. I can print from LR easier than from PS, make a movie, design book, run and save a slide show or just turn off.

Once the concept of how Lightroom works is understood, learning curve is minimal - its getting that concept that many find difficult.

Where did you get your statistics because I can't find them in a Google search.

I am a member of three in-person photography clubs here, with a membership of around 3,450 people right now. At my egging back in November 2013 with all the Adobe Cloud brouhaha, we ran a poll in the three clubs asking which software programs people used and whether or not they considered themselves snapshooters, amateurs, semi-professionals, or professionals.

83% of our snapshooters used Lightroom exclusively.
71% of our amateurs used Lightroom exclusively.
58% of our semi-professionals used Lightroom exclusively.
22% of our professionals used Lightroom exclusively.

2% of our snapshooters used Photoshop exclusively.
9% of our amateurs used Photoshop exclusively.
21% of our semi-professionals used Photoshop exclusively.
62% of our professionals used Photoshop exclusively.

The other percentages included those who used other programs exclusively (Elements, PaintShop Pro, GIMP, Picasa, Aperture, ACDsee, etc) and those who used a combination of programs, such as Lightroom & Photoshop.

Although we have to be semi-rich to live in San Diego and California, I do think those results would be similar in any other state.

With the Internet, I was able to reach all 3,450 people, and because I offered a free Photographic Art creation of mine to respondents, I got responses from 3,451 people (one lady's high school son responded so he could get Photographic Art of his beloved dog, free).

To help respondents with categorizing, I offered this:
Snapshooters don't have a DSLR camera.
Amateurs have a DSLR camera.
Semi-professionals make some money each month from photography.
Professionals make more than 50% of their monthly income EACH MONTH from photography.

For software categorizing, I offered this:
Use Lightroom exclusively.
Use Elements exclusively.
Use Photoshop exclusively.
Use PaintShop exclusively.
Use any other program exclusively.
Use a combination of programs, such as Lightroom and Photoshop.

PS which includes Adobe Bridge and Adobe Camera Raw does not alter the original file. Let me repeat, if you open up the original file of whatever raw file type in Bridge, ACR and then PS, the original is untouched. When the file is in PS, you will likely save it as a Photoshop file psd or other but you can not save over the original raw file. There is no option in PS to do so. When leaving PS the file is saved in a new format. You are left with two images - the raw file and the new file edited in PS. This is preferred.

You don't always convert a raw file after raw processing to jpeg. tiff or other. The original file remains with additional xmp or embedded file documenting the raw processing you have done. All of which can be reset if necessary but the raw file remains intact.

I suspect over 90% of UHH users shoot jpeg.

So your point, while correct, doesn't apply to them. Each time you edit and save a jpeg file in Photoshop you degrade it.

Of course you can (as I did when I used Elements) always use "save as". Also, it is correct that if you save as a psd file instead of a jpeg the original jpeg isn't affected. Some get the mistaken idea that opening and closing jpeg files causes distortion. It doesn't. It is only when you save as a jpeg that you lose information.

I noticed you own an D800e. I also noticed you pretty much know what you are talking about. So would you tell me how you like the D800e? i am thinking of buying one, I am using the D700 right now and I like it a lot. Do you have challenges with larger files, do you shoot the larger files or 'tone it down' sometimes?
Is the workflow slower because of these. What is the highest ISO this camera can handle and still look really good.
I get a lot of assignments and shoot every day, it's a big decision so my questions are serious.
I respect your feedback on PS and LR, I feel the same.
Looking forward to your response and thanking you in advance.