I usually shop at Safeway and they ALWAYS ask if I need help out. I take it depending on where I parked and how much I bought. The parking lot is slanted in some places and it's difficult to hold the cart and load groceries in the trunk at the same time. I try not to park there, but sometimes have no choice.
Oh, and if it's busy I'll bag groceries and/or load the full bags into the cart for the bagger.
I usually return the cart, because I try to park as close as possible to it.
Now, I am guilty of the being on the phone thing. BUT, I have an ear piece and I told my mom (on the other end of the phone) that I was checking out. So while I was checking out I didn't talk to her on the phone. She just waited until I was done to resume the convo. And that time I included the cashier and my mom in a conversation. It was funny! The girl was very nice.

I don't have too many of the issues described here. Not too often anyway. People are always fairly polite, at least that I notice. Maybe I just ignore the rude people. LOL