I live in the UK and play at an online casino once a month for some £1000. For me personally, would be no reason to search for some, very likely, scam UK unlicensed casinos or bookies because I can register in minutes without account verification on any UK high street bookie sites and deposit with PayPal and if I win, get paid in seconds. And get paid guaranteed (99.999%). Plus big UK bookies don't piss around much with the identity confirmation as it seems like they pull data about the player from some third-party source.
However, there are people who gam- stopped themselves without realizing that they won't be able to register and play on any UK casino site for a certain period of time. Therefore, after some time, these people start searching for something that can accept them. But i reckon, the promotion of unlicensed shit sites to players with gambling problems is bad, bad, BAD.