Why Do Women Shave Their Armpits And Men Don't?

Because men do not like hairy women.

Both males and females shave their armpit but males usually shave after long interval. Women shave armpit regularly because they have to wear sleeveless shirts and armpit hairs give bad smell. That is why ladies shave their armpit regularly than females.

Why do women have to wear bathing suits with
tops when males don't?
Unshaven armpits (and hairy legs) on women
aren't socially excepted.   On the other hand,
only 'he men' have hair on their chests
(and other places).    Men can have hair
can look good and a man who has clean
personal habits can smell of sweat and not
be overly offensive.   He's seen as a working man.
Women with hair look...ummm.
Well, it's not my style.
I shave for cleanliness.  Hair there collects and
holds sweat. And a woman who smells of
sweat isn't as socially acceptable as a man is.

Because they'd look too much like an ape.

It's a personal hygene issue,that women need to be properly cleansed

A woman wants to be more feminine. It's gross to have hairy armpits.

Hair below the neck (on men) is considered to be "sexy" by some women, whereas many men prefer for their women to be hairless, from the neck down.

Hair on women below the neck, IMHO, just isn't attractive.