The big worry is that most computers running Win10 don’t meet the requirements to run 11. If they drop support for 10, then a huge number of computers that are functioning just fine suddenly start becoming increasingly less safe to use and the only fix is to throw them away.
When asked to choose between convenience and security, a lot of people will choose convenience. Staying on the computer you already have as long as it seems to work fine is very convenient. I still occasionally see computers running Windows 7 for no reason other than that the owner can’t be bothered to make a change.