Would you let your small children go commando if that's what they wanted?

My 4 year old seems to prefer not wearing underwear. He's more happy to wear his boxers than other types, but still he'd rather just skip them. I honestly don't know if it's just a "one extra thing to put on that takes time so not wearing them is totally faster" or if he really doesn't like them, but I suppose it doesn't much matter. Would you let your kids in a similar situation just not wear underwear or would you make underwear just as mandatory as the pants?