Because they must also comply with the local countries law.
The local country gives women 1 day a month they must use during the month, and it’s no questions asked.
So, the company’s solution is to give the same benefit to the men.
No, they don’t HAVE to use it. They MAY use it, once a month.
I certainly wouldn’t. Few people have that much trouble with menstruation. It’s not all it’s cracked up to be by either sex in popular culture.