It's also much easier to coordinate activities with others with clocks, especially if those other people live in other time zones. "Meet me at sunrise" is a wide window.
Except when part of the world undergoes a change in the clocks weeks before other parts of the world does, so now the world has to deal with the same change twice. So this makes it 4 times a year the world has to deal with the confusion, not just twice. Hell, I'm only familiar with US/UK, so maybe it's even more???
