I used to love early morning runs. Best way to start the day. Felt like I was on hold, waiting to get my run in, if I didn't kick off the day with a run. That habit was borne mostly out of necessity, though. When you start doubling, running before work is just the only practical option.
But during and after the pandemic, I discovered midday runs. And wow, what a difference it makes. Now I get up at the same time, have breakfast and coffee, and get in a couple of good hours of work (usually my most productive hours of the day, unless meetings steal my time) before getting out for my runs between 10-11 AM.
I feel som much better. It's been a game changer, especially when it comes to workouts. It's a luxury, though, which depends on having the opportunity to work from home, and take a 60-90 minutes midday break.
During the weekends I can't just disappear for a few hours in the middle of the day, so my long runs still happen in the early AM. Even if, from a training perspective, I would much prefer to do them a few hours later.
To answer your question, it's mainly due to necessity. If you're doubling, you have to run before work. And if you're not, I still pick early hours 10 out of 10 times as opposed to having to get out at night, when I'm tired from a long day of working or whatever.