There's a guy on YouTube I like to watch who married a woman while he lived in China. They actually had to flee from China, as the government there finally had enough of his YT posts.
But he and his wife had different opinions on when is the best time to take a shower.
Americans favor the morning shower. But she argued that it made more sense to shower before bed, so you do not carry the grime of the day into bed with you.
I think the Chinese have a point on that one. There is just some culturally American thing about the morning prep before going out to face the world.
I think he might have married my ex.
She thought as you're pointing out, best to shower/bathe before bed so your bed is cleaner. Also saves time in the morning.
But to me, showering before going to bed is kind of "wasting clean state": you're getting yourself in an optimal hygiene state for no one but your bed, or whoever is in it, which is (hopefully) a much smaller number of people than whoever you are interacting with professionally.
I can see both perspectives. It's probably just habit but I think the morning shower helps me wake up. I noticed something similar when I started swimming in the morning; it's the only type of exercise I like to do in the morning.