I wonder how many people actually know what the true purpose of a VPN is. But I guess if you have all these youtubers telling you how totally and absolutely they're using x as their VPN service, which of couse is in no way whatsoever scripted and as such provided by the respective advertising company, then its easy to believe that VPNs main focus is privacy.
Instead of giving Google and co the data who then sell it to advertisers and who knows who, you're just sending it to another company. Sure, some may not sell. But even if they don't: the more popular these services become the more lucrative it is to leak that data. It's not a surefire way to protect privacy, it's the hope that they keep their promise.