...and this is how you keep people using mainstream services instead of FOSS / privacy respecting ones.
The actual answer is convenience and not wanting to make their life more difficult, which brings ignorance into it.
Not everyone is ready to flip their whole digital life upside down based on the privacy principles you and I care about - that's why I too use the approach the parent commenter mentioned, and I'm also okay with people who just won't make any switches, because while I don't support it, I understand it.
The long and short of it is don't think of this as "us vs them" - we're all people together and understanding and gently making people aware of these privacy principles and giving them realistic private solutions is, in my opinion, way more effective than saying "fuck 'em"
Linux Mint Debian Edition (LMDE) is my pick.
I've got two study laptops and apart from Tailscale giving me some grief very recently with DNS resolution, I literally haven't had any problems with either machine. Both have been going for 1.5 years.
I like the LMDE route for the DE already having pretty decent defaults and not requiring much tweaking from the get-go. Xfce (as it ships by default in Debian) absolutely works, but I end up spending an hour theming it and adding panel applets and rearranging everything so that it... ends up looking similar to Cinnamon anyway, because default Xfce looks horrible in my opinion