Why do boys and girls wear different types of underwear

That's because boys and girls are different genders. I mean boys can wear girls underwears and girls can wear boys underwears which is acceptable. But Both of them are different type of people. You know what I mean by that right? Bys and girls genders have different kinds of its needs.

Both genders have different needs. If you take a look at men it would make more sense for them to wear boxers rather than a girls underclothes.