[exue]

Mainly because it's easier to get one government to shift their hours and thus the hours of everyone, businesses, government services, etc. at the same time, rather than relying on everyone to make a local distinction.

Though sometimes (like in Western China, where time is really off), businesses run on a 'de facto' local time zone (10-7 Beijing) rather than say 8-5 Beijing time

Similarly, the overall preference seems to be to shift things to a later time rather than earlier