Because people's daily cycles are tied to the orbit of the sun. It's nice to have a measurement of that. With our current system, noon is the middle of the day.

Because people's daily cycles are tied to the orbit of the sun. It's nice to have a measurement of that. With our current system, noon is the middle of the day. So 12 feels like a nice time to schedule lunch. And 6 feels like a nice time to have dinner. And if you say something is happening at 10, I know it will be dark. If you say you were up at 3 am, I know that was very late, no matter where on the Earth you are referring to. I don't need to adjust my sense of time whenever I change timezones. 12 is always roughly the middle of the day no matter where you are. I don't want to like DST because it seems so inelegant. But it does give people an extra hour of sunlight. And I think that is a very desirable thing. There are a lot of mental health benefits associated with outdoor activities and exposure to sunlight. I have personally noticed my mood is very affected by the weather and whether I'm in sunlight.