Yes, but it's just one of the factors, and actually all major user-facing OSes do care about boot times. Other factors are the design by committee and platform

Yes, but it's just one of the factors, and actually all major user-facing OSes do care about boot times. Other factors are the design by committee and platform fragmentation. Hardware manufacturers don't care about initialization times, and standard makers are issuing insanely complex specifications with lots of compatibility cruft and edge cases.