Im obsessed with the fairy clan and I still am to this day! So if you watched Seven Deadly Sins then you should know about this. So I have read in the Manga of sds (Extra Chapter 17) and Elaine and Ban want shopping for panties and underwear(for King).

The reason why is because   F A I R I E S     D O N T       W E A R     P A N T I E S  /  U N D E R W E A R S!! 

Btw there called commando (meaning they don't wear underwear. XD I don't think much people remember about Elaine saying she doesn't wear panties and king chuckles saying he wear underwear. The shocks from everyone killed me!

 It is fairies traditions to do that. EVEEYONE FAIRIES DONT WEAR UNDERWEAR/PANTIES!!!

It is just that they don't care about wearing them.