Attention and popularity is one hell of a drug. If I'm running a website (about pretty much anything) and I see my views go up significantly, then that encourages me to work on the site more. And the opposite is true if no one gives a toss.
Criminals and scumbags are just as human as the rest of us, and their motivations are often the same. They want popularity, friends, money, fame and power. Even at the possible expense of getting caught doing whatever illegal activity they're doing at the time (like those kids posting pictures of them taking drugs on Facebook or psychos boasting about their crimes on social media sites).
They'll stop doing that stuff when there's no pay off. When there's no audience left.
They will likely stop running a website, but not abusing children. Child abuse was a thing even before photography existed, way before Tor and Internet emerged.
Taking drugs is not a crime.
Making possession illegal is a measure to reduce consumption and harm producers. It introduces "victimless crime" that does not harm others per se.
It is doubtful that hits for .onion sites are enough to encourage someone to produce CP. Download and seed more, maybe. But producing more just because someone downloads it?
> literal money from paid purchases or subscriptions
Subscriptions work mostly because of copyright. If content is available free of charge elsewhere, it is not profitable. Free of charge distribution of existing content will drive its price down. If distribution is banned, it will be cheaper to produce new content than download existing one.
> That's not true of standard copyrighted content. In those cases, distributing it (legally or otherwise) is not encouraging something illegal to be done since producing said content isn't illegal to begin with.
Standard copyrighted content (music etc.) is different because it is possible to support artists by buying tickets for live performances, so piracy may benefit them. It is not true for CP.