It's the advantage of centralization. Instead of every entity changing their operational hours, they peg it to a common standard, and simply change the standar

It's the advantage of centralization. Instead of every entity changing their operational hours, they peg it to a common standard, and simply change the standard. It's a layer of indirection. By doing it this way, we keep things in synch, like business hours matching school hours matching transit timetables and so on. If every one of them changed their hours separately, we'd have a much greater mess than the less-bad current approach to daylight time. Whether we want the functionality at all (to adjust human activities based on sunlight hours) is a separate question. Given that we do, DST is a useful abstraction compared to going without it.