I guess the thing that worries me is more so population effect versus direct personal ones. When companies know they can extract useful information from a source, there becomes a market for the information, which further incentivizes others to collect the information. The other thing is that even if you don't care about ads, I assume you care at least about browsing privacy. The main reason why GDPR was even passed was data privacy and security.It is difficult to know who has what personal information and for how long they keep it. Because of that, it just takes one breach where suddenly your email/username/personal information, along with all of your browsing activity, gets leaked. This wouldn't only be the ones that you purposely entered your email address in; it just takes one site to have your cookie "fingerprint" and email connected, and suddenly all the sites that recorded that fingerprint will have a record that you visited them. All in all, I agree that there is a low chance of personal harm to you, but I look at it like putting motor oil in the storm drain. "Low trust" cultures where people only care about the direct effects of actions to themselves instead of society as a whole always fare worse than cultures where everyone sets a standard of what is acceptable or not.