Oomis, I think its a generational thing.
We ALWAYS open doors for our grandparents, no matter what. It wouldn’t occur to me (or DH really) to open for either of our parents, unless there was a reason to (hands are full, dirty, or something else). This is probably a product of growing up with automatic locks in cars – its no longer a huge deal.
I would automatically hold the door open for someone to let them through – anyone really. I think that’s more common courtesy than anything. And I expect others to do so as well, without turning them into a pretzel.