Underwear offers a barrier that keeps residual urine and feces particals from absorbing directly into your pants.
People that dont wear underwear let their bodily fluids make direct contact with their pants, and then expose them directly to any surfaces their bits might touch.
Not wearing underwear is unhygienic.
Bruh, your underwear makes direct contact with your skin. Whether it’s pants or a layer in between, the result is the same that the barrier carries your pee and poo and it’s in contact with your skin.