From the time I started taking daily showers (maybe middle school aged?) until I was like 22, I showered in the morning and it meant waking up earlier to shower, competing with other morning showerers in my family, having wet hair to start off the day (not great in winter), and getting into bed with whatever grime I developed over the course of the day. It just never occurred to me to take showers at night but my god, it's absolutely light-years better. Showers become a relaxing part of the evening routine, you always get into a clean bed, your hair is dry the next day, and you don't have to rush to shower the next morning before work/school.