Why are men called womanizers but women are not called manizers?

Because some people think it would be rude to call a man a whore.

Because being man is thing of pride. They say if you are not manly, nothing can make you manly.

So manizer is insulting.

Because it doesn't sound like a real word. Double standards do not apply here.

Double standard perhaps?

because there are other names to describe them, like sluts, whores, skanks etc

they have other terms like slvt

guy magnets?