I'm never taking a shower. Don't even think about it.

Other: Both

Morning (although after exercise: I've never understood people who get up, shower, go to the gym, then re-shower – except as a response to specific circumstances).
Night (even if the most strenuous thing one has done is catch up on paperwork, fresh before bed is just nice).

both (night is more important tho)

Light night sweat vs dirt/grime/buckets of sweat/mud/blood/oils/whatever disgusting thing you can think of.

Work at any dirty job like hospitality, construction, medicine or do any sports and you'll see why people shower at night

Night showers, you spend the most time in the day, and it doesn't make sense to just get dirty immediately after cleansing, plus sometimes it's just super chill