Most entertainment industries seem to have moved into a more subscription model with content more personalised so makes sense porn is now in this route. I also think less people are having sex these days, not sure on the stats, more an impression I get from reading online, most young guys struggle with online dating and older guys in sexless marriages, they want to get their kicks and some sort of connection, so they start to simp these girls online. Maybe makes sense to them to pay £30 a month to subscribe to a handful of onlyfan girls to get that. Coronavirus has probably accelerated this trend, I sometimes follow a personal finance forum, I've read a few posts of girls on there who were making small side income on it to now £5k+ a month since lock down and asking for tax advice.
It's not good for punters but realistically will have most impact on the top end of the market, girls with twitter/Instagram following as they can convert this to good income stream on onlyfans rather than fuck guys, won't impact the average hooker who would struggle to compete on the platform.
At least that's all my theory.