Why do Gen Zs so strongly prefer sweatpants over jeans?

I live near a college and a suburb. If I walk past the campus, everyone’s wearing sweatpants (usually gray and loose-fitting) and logoless hoodies. I go to the grocery store, same deal. If I go to Sheetz (gas station which is also a popular hangout), boom, most of the high school or college students (can’t tell who’s who) are in sweatpants when it’s too cold to wear shorts.

Where’d this shift come from? When I was growing up, most of us wore jeans. In college some people wore sweatpants, but they usually had the university logo on them.