If you're wearing a dress, skirt or kilt - not necessarily a problem. But if you wanna keep the pee stains and skid marks off the inside of your jeans, trousers or shorts, I wouldn't recommend going without gitch.
Most of the time I wear skirts or dresses without underwear but if I am wearing pants I will wear them to prevent the seams from chaffing tender areas.
The male thongs definitely leave more room up front, women's panties can be a little too small up there sometimes, just need to find the right ones; I prefer them as they're generally cuter with some lace and such... These are men's.