Except I'm not saying there is only X and Y. I'm saying there is AAAAA-ZZZZZ and people working on problem XYZAB would be able to help actually push these operating systems forward if they chose another problem they also found interesting. I do not believe that it is only possible for these people to be interested in a single problem. I think these people can be motivated to find another problem more interesting.

> I think these people can be motivated to find another problem more interesting.

You can pay them I guess, usually a good motivator.