Ear warms?

I saw my human do something odd this morning.
He put a fluffy thing over his head, so that it also covered his ears.
I've seen other humans do this, too.

This must be to give him ear warms.

I don't understand. My ears are always warm as I has fur on them.
Why don't humans just grow fur on their ears?
Why don't they grow their head fur over their ears?

Humans are so odd.