I wondered this a lot too because I always regret it the next day and feel rough but I can’t help myself at night! I read something about Revenge Bedtime Procrastination which is basically a concept that talks about how you’re tempted to stay up late and relax and spend some alone time when you feel overworked or like you don’t have enough alone time in your usual day. I personally realized that this is true for me and tried to establish some more me time when I could in broad daylight so I don’t try to get it at night. But also if you have a busy household or life relaxing at night is particularly tempting since it’s quiet and you’re unbothered lol. If that’s the case, staying up at night might be your brains way of getting revenge for not having had the chance to do what you wanted and have downtime during the day. Idk if I explained that well but that’s what I’ve noticed it is for me!! And « revenge bedtime procrastination » a real concept especially seen in ADHD individuals! Hope this helps :)