Perplexities related to fashion: why are people wearing hat/beanieinside their houses in summer time?

I noticed this for the last couple of years: people wearing hat inside the house. Look at the picture below, this girl is in California, in an area that now are 22 degrees, so cold for them, but warm for the rest of the world. Why the hell wearing a beanie?

Or this picture ,where people are in the house, but wearing a hat.

What is the point?  Do they have a cold head?