Is it just where I live or do people shop for groceries in their PJ's?

I've seen people wear "clothes" out in public (not just the grocery store, but movie theaters, too) that I wouldn't wear at home. I first noticed it with students at the university I work at a few years ago where they'd come to the dining hall, the library and even cl in their pajamas and slippers. I figured it was a trend that would die out. Instead it has proliferated. I see it as a lack of self-respect.