Why does Facebook seem to prefer Edge or Chrome browser?

Just now I went to Facebook in my Safari browser, then launched Messenger. The first thing I saw (and I've seen this before from time to time) was a notice that "You may need to update your browser—End-to-end encrypted chats won't appear in this browser. Try updating your browser or use another one."

Well, the other one they seem to prefer might be Microsoft's Edge or Google's Chrome. First, I'm very careful to keep my browser (Safari) fully up-to-date. Second, I don't feel I should have to keep a spare browser on hand to cater to Facebook's apparent whims.

I'll look forward to reading anyone else's thoughts on this matter.