You guys must not do a lot of off roading or if you do you are just out driving around in the dirt or mud.. When you get stuck on a trail, you absolutely dont want to be winched backwards because you are trying to get somewhere (down a trail, over an obstacle, etc)
If you winch backwards and get unstuck, unless you have another path around what you got stuck in you are going to have to go right back through it again.. The rear winch is good for recovering other people who are often behind you on a trail and are coming with you or in the same direction. Same reason they would want a front winch if you did not have a rear one, though a proper snatch strap or tow strap could suffice in that situation.
In the off roading circles I run in, almost no one has a rear winch and almost everyone has a front winch. The idea scenario IMO would be having both front and rear winches or better yet a central winch with fairleads on each end of the truck, thereby keeping all the cables and motors and such out of harms way, out of the mud, etc.. that a front or rear mounted winch would see.