Virtually every company public and private in the US use Gmail or Outlook. Interesting that your circle is using alternatives but you're still very much an outlier. Like to an extreme that's very surprising to hear. For personal use nearly 90%+ of global market share splits between Gmail and Apple with nearly 60% of email in the US being Gmail based and Apple holding most of the rest.

But it's not shit for them. It's always works, never down, works fast, and reliably on the computers/laptops/phones etc. Most people could not give a monkies if they are tracking cookies. It's easy to use so they have no reason to move away. Not everyone is a tech nerd who looks for other solutions which are normally more complex. They just want something that works, and that is why gmail/google is popular.