I have a day job myself, but it still doesn't change that I make my cut-off at 8pm.
I wake up early every day, often 6am, and if I had a good night's sleep, 5:30am before the alarm clock goes off.
Another reason was because it gives most people time to get home, have supper, and don't have enough time to get intoxicated before I am not available to see people in an altered mindset.
I tried when I started to be available 24hrs, and sleep patterns were impossible. Then after a bad expierience happened in the early dark of winter night, I refused to ever accept a night appointment ever again, unless it is a duo. (I'm not alone, and the price becomes worth the nighttime discomfort, especially with providers I am already familiar with, the nervousness can disappear.)
It's not even about who it is at night. I have regulars I no longer see, because they are only able to at night, and I won't make appointments past 8pm. Only exception when alone being if it was an 8pm appointment, and I am running late, and have no plans later, except home to bed.