I used to authoritatively state rules that existed in my own head. I no longer do this.

I always liked busting through the little social candy shell in the gym. Offering to let people work in on a scarce piece of equipment could lead to chit-chatting about whatever. It's nice! When you have about 3 minutes to rest in between sets there's time to let someone else work and talk a bit.

Varies wildly. Some people are there with this attitude. For others it's more of a social time with occasional breaks to do a workout set.