So weirdly enough, there may be a good reason these brands do not and probably wont go after these creators:
Parody laws
Much like they do with innovation(they ALWAYS innovate first), the porn industry as a whole, act together with a vengeance against lawsuits that will affect the entire industry. When porn parodies were in their hay day after 'Batman XXX: A Porn Parody' (25 years ago), the brands wanted the adult industry to keep their names out of their mouths, but the very few lawsuits the brands brought, they lost. Hard. No big name brand is going to go after
Lil' Cosplay Slut. Ever.
It doesn't matter if 'cosplay' is literally in her name, she is legally protected by US parody laws (which are hardcore as hell) It doesn't matter if she's
slutty Pikachu,
Gwen Stacy getting railed, or
Hermione and
her very magical wand, going after her or other creators for this type of copyrighted IP would be nigh suicidal.
And yes there is case law that states that just because it's dirty doesn't make it a parody, the IP holders would have to prove beyond a reasonable doubt that this type of use is affecting there market (it doesn't), and they would have to do it with EVERY SINGLE creator using their IP...on a case by case basis... and do it in such a way that doesn't bring more attention to the porn versions than their own IP. This is a no win scenario for them.
My guess is for every one they would win, there would be 5 that they lost. All it would really do would be to force a lot of creators to use the word parody on their clips or at least somewhere on their site page.
On the other hand, the audio piracy is on much firmer ground with possible lawsuits and copyright claims.
AND THEY WILL NEVER PURSUE THEM EVER!
EVER!!! Not unless a particular creators work is financially harming them or somehow hurting their IP.
Drugs, Sex, and Rock'n'Roll is an actual thing. Almost every popular musician and industry exec has dated a 'model' at some point, be it super or adult. Every strip club uses music they don't license. The adult industry knows where the music industry has their secrets buried, and they will bury that industry with those secrets if they start coming after the creators wholesale. Even if they don't use this connection against them, they have other ways of hitting the music industry where it hurts...
Imagine being a music exec and having to have the following conversation with your talent:
Music Exec:
"Hey Mick. Hey Jay. Hello every up and coming rapper and band, thanks for joining this call. So I've got good news and bad news. The good news is, we Dmca'd every single illegal user of your music..."
"The bad news is that included the adult industry, and you're all banned from every strip club in the country (at the very least), all the big booty ho's have dropped out of any upcoming videos and performances, which include bachelor parties and club gigs. Also I'm pretty sure any side chicks or babies mama's are calling up your wifie right now to inform them of the situation..."
"And remember, before you come to kill us, we did this for you...and I have to go leave the country right now before my wife and side piece come and merc me...I really shouldn't have made my sister in law my mistress, but she had the DD's and no gag reflex...anyway I have got to go, every member of Aerosmith is outside of my office with a Tesla flame thrower and I need to run...literally."