People will try to pay you in drugs because it's cheaper for them than cash + they figure that if you're gonna go for the okey-doke, hey, why not. They save money, you get high, everybody's happy.
Besides, if you're an addict and not just a Get High Boy, hey, there you go, they can get you to play the next gig for that, and the next, and the next...all the gigs, until you fuck up once too often or once too badly. And then they can just find another chump.
This shit ain't pretty, this getting paid business. Just play the records.