Can you ride on the edge of the white line forever? Neat skill to have when you are bumping knuckles with another rider. Or when you are trying to keep your bike on half an inch of pavement between someone else's wheel and the edge of the road. Neat tricks, yes?

That's what rollers help you achieve. Fine bike control is a skill not many rec riders have, and, I would say, is the defining feature separating racers from recreational riders. Why do I never fear another rider's bike handling skills in a pack or pace line? I mean, I'll sit an inch off anyone's wheel, regardless if beginner or pro. It's because I have these skills. Most don't. Rollers are extremely helpful in obtaining these skills.

EDIT: from the comments here, it is apparent that not only do rec riders not have fine bike handling skills, they are not even aware they exist...