I think that you are missing the point. Mirrorless is much more than a pissing contest. Mirrorless is much simpler than SLR mechanically. It is also smaller and lighter as others have mentioned, but the main thing is "simpler mechanics" = "more reliable". There are fewer moving parts to break or adjust. Eventually we will see the mechanical shutter go by the wayside as well. We already see them in use for the higher speed shots on many cameras, many also offer a silent mode in their menus.

Regular dSLR cameras are not mirrorless. Do not confuse raising the mirror to mirrorless. Mirrorless bodies have no mirror, period.
One of the greatest advantages of mirrorless bodies is that they are small and the majority of them light which makes them easy to carry all day without feeling tired. In a very small bag or a purse it is very possible to fit a mirrorless body with three lenses.
Another thing that separates mirrorless from dSLR is the distance from the rear of the lens to the sensor plane, called before film plane. The distance is pretty short what makes for sharper images.
I do not know about other brands because I use Nikon but try in live view to see if you can see the changes that take place when you change exposure, something that Olympus offer and I do not know about other mirrorless bodies.
Not all Nikon cameras can do that.

Mirrorless is now a word. It’s okay to drop the hyphen and the quotes.

There are many, many important reasons to use mirrorless cameras. They’ve all been mentioned here, before. Do a search.

My journey from film to digital, SLR to dSLR to mirrorless, spans 50 years, this coming August. 33 of those were spent working in nine different roles for three of the largest photography companies in the world (One “ate” the other “ate” the other over the years). I used every film format from 4x5 down to Minox, plus APS-C and full frame Canons and Nikons.

So, from that perspective, I have to say that the transition to mirrorless makes more sense *for some* than most folks realize until they try it. The advantages outweigh the disadvantages for me in most respects.

However, high end dSLRs still work better for sports action, birds in flight, and wildlife photography. The advantage does get slimmer as technology advances, however.

I made the switch to mirrorless because I had a specific set of needs that were best met with specific mirrorless equipment. Your situation may vary!

GAS is a problem unless you can afford it. If your current system does what needs to be done, keep it, use it, and have the courage to be confident in your choice.

Gee ...

Based on your apparent attempt at pedantry with regard to the addition-or-lack of a hypen then I think that the majority of the users who have a DSLR should possibly classify-and-refer to their cameras as point-and-shoot cameras with-or-without-the-hypen UNLESS they are using a vintage, manual focus lens IF you are trying to eliminate extraneous descriptors ...

BTW. Clearly (!?!), IMO, the OP was trying to make a point that some of the benefits of a true mirrorless camera can be achieved with a person's current DSLR ...

Ergo, using/(i.e., image viewing ...) a DSLR sans mirror ... hence, his use of the hyphenated "mirror-less" instead of "mirrorless."

Yes, you certainly can get some of the benefits of mirrorless cameras if you lock up the mirror and use live view mode on a dSLR.

I don't think most people would call a dSLR mirrorless or mirror-less. [In my best South Cacalaky redneck voice:] "It has that flippy-flappy thang" in it that's irritated me since 1968. Lock it up for live view, and the AF system suffers. Lock it up, and you can't see the LCD screen very well in bright sun. Lock it up in a theatre, and you piss off the patrons beside you. And Hoodman? Meh.

As just an enthusiast, I must say that switching from 40 years of Canon SLR's (started with Pellix 1972) I am having more fun with Sony system than I could have ever imagined. It is just a hobby, I was able to convert my Canon stuff to Sony without too large a financial hit (thank you Ebay and Craigs List) and the smaller size, optical quality have made it for me extremely worth while. Gave up on adapting my Canon glass to Sony because native lenses were superior. Learning new skills everyday, trying video, learning photoshop and lightroom, printing for my own enjoyment. Filling my retirement days with real joy and pleasure.