why would you want to wheelie a softail? um.... for the same reason you do a burn out, see just how fast you can go, try to get a little air off that "hump" on the country road, race your buddy, stand up on your bike and go from the back of the pack to the front mooning all your buddies, haul two fat chicks at the same time, reach over and hit a buddies kill switch while riding, ride two a breast thru a twisty road with no hands... sure I'm missing a bunch.
mainly because stupid is soooooo much fun! for me anyway.
first time I did one on my fsxtd (95") was not on purpose. warm tire, hot asphalt and intended to do a rolling burn out. did a few more after that, but it just sounded like my front end was going to snap when it came down. I never got it over 2 foot off the ground.