In the US, I suspect that the idealized norm is once a day. In Japan, I am given to understand bathing is likely to be much more common -- minimum once a day, and twice being more common, at least as the idealized norm. I don't know what the idealized norm is for other cultures, and I could be wrong about the Japan one.

It generally takes me more than a day to feel really grubby. *shrug* Peoples! They are all different! O:>