I think there has been a huge increase in the past 10 years, and I believe it's mostly about economics and generations, much as DL hates to hear about Boomers etc.
2 cohorts ago, the silent generation, everybody was too closeted, and opportunities were few. Their children, the Boomers, were slinging ass for cash mostly in major cities in the 60s-70s. I think after that, the Boomers sublimated their desires by pursuing money, or they married and went into the closet.
Boomers were mostly willing to fuck their youthful peers, most of whom were doing well financially, so there wasn't as much of this daddy nonsense and little need for financial exchange. AIDS took out a bunch more guys. For a couple decades at least, from the mid-80s until the mid-2000s, I don't think there was a ton of hustling going on for these reasons - fucking peers and general sex paranoia.
I was one of the 90s hustlers, and I was popular, in part because there weren't many guys doing it, because my young generation (x) was much smaller than the older generation looking for sex (boomers). You had to be either real horny/kinky to want to hire a hustler, or you had to be in a rather difficult situation socially (closeted, isolated, lonely) in order to need the services of one.
By the 00s and 10s, things started changing a lot. Boomers were getting old, but they had Viagra. They weren't giving up on sex. Better nutrition and healthcare meant people were staying hard older. They had lots of disposable income. As has been discussed to death already, Boomers are a spoiled, self-centered and immature bunch. These types tend to want to hook up with youngsters, because arrested development.
In the earlier days (90s) of Gay.com, AOL, later A4A and Craigslist, there was hooking up, but not much hustling. In particular, gay.com and AOL would take down your profile if you used it for escorting. A post advertising oneself for rent was uncommon, and I lived in several medium to large US cities during this time. By the 00s, the Millennials were ripe for fucking, and were mostly fucking each other. But the eldertards went after them with gusto. (There may also have been a bit of a delay in eldergays adopting the ways of online dating.)
I remember rebuffing the eldergays. They were very pissed off about this. They demanded that people do as they want, and that includes sex - in my mind, Trump is a perfect example of an addled, spoiled Boomer. The millennials weren't doing real well financially. So the olds figured it out - they'd pay for sex from young people.
Where I was living at the time, this became a thing around 2010. The recession was still a problem. Many guys would advertise they were looking for work. But I'm sure they got offered sex. Soon the ads were blatantly asking for or offering sex for sale. A contractor I knew made more money fucking men and women than doing bathroom remodels. Remember that this was illegal activity and there was no precedent for publicly putting oneself out there as a john or hustler.
Nevertheless, soon it was understood law enforcement didn't care, and by 2012, roses, gen and daddy were all over Backpage, CL, and the apps.