[nonasktell]

Well it:

-cuts their profits in half or more because they have to pay for the proxies(or if they own them they can't sell them since they need them)

-it prevents most low skilled people from doing it

-it prevents them from doing on it on an infinite scale, AWS have more than a 100 millions IPs, it's rare to see a grey market proxy provider with more than a few millions clean IPs, and it usually cost like 40 cents per IP, where it can be FREE on AWS

You add basic protection against headless browsers, behavioral analysis etc...And now 99% of the people who can fool you are already making 6 figures in legitimate jobs and won't risk 10 years of jail to earn just a bit more money.