Naver Webtoon, for one, has rolled out an in-house tool named Toon Radar that embeds invisible watermarks in each chapter. When a pirated copy turns up online, the watermark allows the company to trace it back to the specific account that downloaded it.
Well, the thing is even if you trace it back to an account, what do you do then? Only a single pirate with a bit of opsec knowledge needs to have an account with e.g. a stolen credit card or whatever, and then they can just leak everything with no consequences…
Still makes it effectively 1000x harder than just having the same account forever. Because now you need a new stolen credit card account for every new release.