Personally, I'd much rather have a decent EPC and get paid honestly and in a timely fashion, but to answer your OP, yeah, some guys demand it so it's best to have something on tap- just make it attractive and I also recommend have some field leveling "mini" contests that anyone can win, no matter how small their list etc.

If you track it, most aff contests are won by big guns who can bring major heat, and that can turn off a lot of small fry who can bring a lot of sales if they are motivated, believe it or not

Motivate them ALL by giving them a shot at a "timed" contest or something else that doesn't depend on big reach- be creative, like the sale closest to noon wins... first sale to a last name beginning with "R" on Wednesday between noon and midnight... etc. Whatever. Pull a name out of a hat out of all affiliates who have driven at least one sale. Have some fun!