Before kids, it was nothing.
Now, in the summer, it's a tank top & panties. In the winter, most of the time, it's a tank top & panties as well, unless it's really cold.
If it's really cold, I might start out in a tank top & PJ pants, but, after I get warm, the PJ pants come off. Same way w/ socks. If my feet are cold when I go to sleep, I'll put on pair of socks, but I really can't sleep in socks, so, after a few minutes, the socks are off too.
Before kids, DH never wore anything to bed either. Now, he wears a pair of underwear.
I have some PJ sets that I take on vacation or wear if we have company.