You can get up whenever you want. The point is that most people live and work regular hours, and those regular hours are now one hour earlier as compared to the actual diurnal cycle. If you work 8 to 5, you can't just come in at 7 and leave at 4 and say "Hey, I live my life one hour ahead of you. I don't have to change my clock." Since that's what most people would prefer, it's easier to actually make the official time one hour later.