Yes; if I am feeling low, and can't be bothered to change. But that it only because I wear leggings and a t-shirt to bed, which is also cceptable day wear. If they were proper pyjamas, then no I wouldn't.
Yes I hate that too. Just make a bloody phone call, a warning. My friends usually get a bit annoyed with me if I am in the middle of something and I let them know that I have no intention of putting the kettle on until I am finished doing whatever I am in the middle of.
It is just bad manners to do the "just popped in" thing. I wouldn't dream of doing it to them.
One friend does it at dinner time -but always when we are having left overs - it really, really irritates me.