Who puts their speakers right up against the back wall and why?

Aside from Klipsch corner speakers, who does this?
It all depends on the speaker. I’ve heard the Wilson Tiny Tots up against the wall and they sounded fantastic. If your speakers are rear ported, you want them to breathe, if they are front ported, then you have options. I have large floor standing speakers and they are 7’ from the wall behind them.
No matter where you place the speakers, you are always going to have reflection issues: 1st reflection, 2nd reflection, ceiling and floor. All reflections should be dealt with.
ASC aren’t the only vendor that makes bass traps. I use both ASC and GIK bass traps. Check out both of these companies plus acoustic field and others.
Who puts speakers against a wall? People who live in real houses and live real lives! Three cheers for Larsen. Have you heard them? They are designed to put out a quarter hemisphere of sound. I heard them first at CES a few years ago. Walking by the open door of the hotel room, they sounded wonderful. If I placed speakers "three feet from the side walls and at least 30 inches from the back wall," I couldn't get to my front door. Speakers have to live with us, not us with them. You can hang oriental rugs, curtains, your wardrobe on the wall behind the speakers. Space them an inch off the wall. It's nice to have a dedicated listening room, but some of us can't afford it. Keep listening!
The Snell Type A2 I had years ago sounded really nice with 4”-6” space from a really solid wall.  A buddy had earlier Snell TypeA speakers without any rear vent or drivers and used them almost against the wall. 
I have a pair of Polk sda speakers that image better than most speakers out there and they were designed to be up against the wall. They even image better than my apogee duetta 2's.