Explain these dumb strategies to me (or maybe I'm the dumb one)

I don't understand the thinking in the NBA that when a team is down by 2 or 3 with around 30 seconds left they don't foul and just hope for a stop. It seems to me the best case scenario is you get the ball back with about five seconds left, but you also run the risk of the other team scoring, effectively ending the game, or they could get an offensive rebound, effectively ending the game. Obviously college is the other end of the spectrum, with the last minute last 20 sometimes, but I agree with that basic philosophy: you want to extend the game as long as possible to give the other team as many opportunities to mess up (miss FTs) and give your team as many possessions as possible (hopefully trading three's for the FTs). They just need to cut down on the timeouts in the college game.