How do you verify 3-SAT? Just plug in the values and check if it evaluates to TRUE? I assume the idea is to pay people to solve NP-hard problems via TX's, which is a kinda neat idea imo.
For various reasons, you probably want to use arithmetic and string operations for encoding certain problens. You could do it in bit operations, but efficiency.
I can't take credit for it -- it's one of those things that was floating around as a usage early on, but the features were killed.