Feet without sandals don't have much interest. Art of feet usually show them from the bottom, which is unappealing as they're wrinkled like an old lady. Sandals show feet from above, where you can see toes and fabric from the shoe dancing beautifully up to the ankle. The toes can have polish on them to put more emphasis of their cuteness. Sandals are meant to worn outside which means the bare body can be appreciated from passerby. The exposed skin presented to outsiders show weakness usually only shown within the house. Sandals also mean Summer, and all the odors that are associated with them.
It's no exaggeration to say that sandals are superior to feet alone.