Hell of a time to run a VPN or a blackmail service... Porn site profiles with activity history + real traceable identities will make the Ashley Madison leak look quaint.
The history is extremely unlikely to be available to the id validator (beyond the domain at most). VPNs can't see the actual history either.
The average PornHub user's history will be full of weird incest shit at the very least, not because of any specific interest in the genre but because so much generic heterosexual porn is labeled as such. Looks really bad for you if it makes the newspaper.
So even "tame" leakage is 100x more embarrassing than it ought to be, and thus snooping on bf/husband's devices to humiliate them over their porn usage is normalized on relationship subreddits. Same goes for them plugging your email address into the password reset form to try to verify whether you have an account on any given site.
Frankly, Stephen King stories are much weirder than any porn. Imagine enjoying watching monsters eating people.