What are the constraints of social etiquette of male white-collar workers on revealing armpit hair?

Not uncivilized. It is normal.

Male white-collar workers don't need to shave their armpits.

Axillary hair will grow faster if it is shaved off.

It's normal to have armpit hair. Those athletes don't show it because of the need of exercise. Axillary hair is easy to accumulate heat because of the large amount of exercise.

But there is no such requirement for white-collar workers, so you are not uncivilized.