Rangefinder film cameras and the lenses for them are considerably more compact... but the selection of lenses for rangefinders was always quite a bit more limited than what was available for SLRs. Both systems commonly had 20/21mm, 24/28, 35/40, 50, 75/85/90 and 135mm... but 200mm and longer lenses for rangefinder were unusual... as were specialty lenses such as ultrawides, fisheye, tilt shift, macro. All those were impractical on cameras relying upon separate viewfinders, rather then the "through the lens" viewing SLRs provide. This difference goes away with mirrorless, because they're TTL, just like SLRs/DSLRs. But are the small cameras practical to use on big lenses? Hard to say. There aren't a lot of "extreme" lenses for mirrorless. We'll see!

But you can resize a higher MP image to a smaller screen size, without resampling. If you take an image from a D800 that is 7,360×4,912 and crop it, without resizing, to 1920x1200, it will "fit" a standard WUXGA HD display, which is also 1920x1200 in resolution, with no resampling needed. In this case Adobe's dpi specification is just a metadata tag without meaning or application.

Also, if you send a higher resolution or lower resolution image to a printer, most printer drivers (or raster image processors) will up/down sample the image to fit the image on the paper at the given resolution. A 6 mp image from a NIkon D70 is 6000x4000. At a desired print resolution of 300 ppi, you can print, without resampling, a 20x13.3 image. Without resampling the image, you can print a much larger image, like 60x40, but at a lower printer resolution of 100 ppi, with the print driver or RIP handling the "resizing" without resampling. However, if you need a higher resolution than the image has provided, say 200 ppi, then you have the option to resample the image to 12,000x8,000 px using an image resizing program, or the resizing algorithms in Photoshop, Lightroom or other image editing software, or let the printer driver/RIP resample it - so that you will be able to have enough "pixels" in the image to meet your image resolution requirement. The issue with up-sampling is that software is used to expand the individual "pixel" spacing, and it uses interpolation to take a good guess at what should be placed to fill in the new space between the old pixels. Resizing software NEVER increases resolution, but the better software will increase the edge contrast, or microcontrast, to give the viewer the perception of greater sharpness.

So, though I usually agree with you, Scotty, on this on I don't agree 100% - you can crop to resize to a given pixel count. It doesn't always have to be resampling.

I probably crop 90% of my images. Frequently it's just one edge (or one edge pair) because I don't like to be limited to a given aspect ratio. Frequently my lens is too short and I have to crop to get the subject I want. (I shoot events so I don't always have time to change lenses, or sometimes even turn the zoom ring). Frequently I leave some room for cropping because then I can take my time to crop the way I want it rather than stand there while a shot evaporates in front of me while I'm trying to decide just how to compost it in the viewfinder.