Why do you think my cats like pants so much?

I usually change into PJs when I get home, and I usually just leave my pants on the bed until I put them away/in the laundry later. My cats always snuggle on my pants. If there’s a sweater or a shirt on the bed as well, they’ll avoid it in favour of the pants. It’s puzzling and weird. It doesn’t matter whether the pants have been worn, either – if I put a freshly-washed pair or a pair that I’ve just taken off on the bed, they’ll sleep on them. They won’t sleep on Mr. Fiance’s pants, either.

Why do you think they do this?