I've moved almost completely to Proton Mail. I expect I'll end up keeping a Google or Outlook account, not for use as a primary account, but as a recovery account or to access other services.
I currently see a lot less value in the google account than outlook, but that's because my family does need access to full blown office. Libre office does 98% of what I need, but on occasion I do need office. An install of 2010 would probably meet that requirement as well. Firefox is set to delete cookies on exit, and I do not ever stay signed into these services.
Does anyone else keep free service email accounts around, and if so, what do you use them for? What's the pit-fall I'm not seeing if I try to restrict them and treat them with the Principle of Least Privileged model?