Dr. Drang already said most of what I would say. What I can add is the perspective of a person who grew up where Daylight Saving Time was standard (California), and who moved to a place where it isn’t used (Japan). Latitude makes a bit of a difference. I grew up around Sacramento (38°33′N) which is nearly 3° farther north than Tokyo (35°41′N). Tokyo’s day on the summer solstice is 17 minutes longer than Sacramento’s. Note that since Tokyo does not use DST, sunrise occurs at a local time an hour and seventeen minutes earlier, and sunset is an hour and a half earlier than Sacramento’s. If they both used the same time offset, Tokyo’s dawn would be at 5:25, only 17 minutes earlier than Sacramento’s.
I’m a natural night-owl. Normally, if I go to sleep at around 01:00, I wake up on my own at about 08:00–09:00, no alarm necessary. If I have to wake up at 06:00, I need an alarm no matter what time I go to bed. Getting older and having kids has adjusted this tendency to some extent, but the lack of DST in Japan still makes my life somewhat miserable in the summer.
The adjustment to the time difference during my first week in Japan was complicated by a homestay. I was in a room with very insubstantial curtains and the dawn light woke me up every day before everyone else in the entire house, including the mom who got up an hour before the kids. I had much the same problem when I finally moved into the housing provided by the school I was working for. I would wake up around 4-something most mornings during the spring and summer. It wasn’t until I had my own place and got blackout curtains that I literally tacked to the walls so that too much light wouldn’t leak in that I was able to sleep until a more “reasonable” hour of 05:00–06:00. Even those measures weren’t enough to adjust my sleep clock much when the rest of the day’s light was telling me that it was much, much “later” in the day than the clocks said.
Without DST, it gets dark ridiculously early during the spring/summer months, feeling barely later than in winter. Adjusting the clock to better fit the actual daylight hours makes an enormous amount of sense, and makes it much easier on people like me who are easily cued to wake by the sun, but who don’t want to get up 3–4 hours before everyone else.