Why did mostly girls?

back in the 2000's, Wore their sweatpants or pajama bottoms over their jeans, I'm not talking about when people put their sweats over their jeans during PE because I understand they don't really want to change for PE, but I'm talking about doing it for no reason, even in the hot summer, back in summer 2003, I was hanging out with a female friend after she got home from school, when she got home she put her or some friends pj bottoms over her jeans and wore them like that all day, and the next time I hung out with her she done it with sweatpants, ever since I've been seeing more people especially girls wearing pjs or sweatpants over their jeans like at school (not PE or PJ Day), and my old neighbor, and others out there, I don't really get it, is it cool or something, to me its just plain weird and a disrespect to jeans lol