It is a dumb bit of ceremony, but the door checker just glances at the card. You could roll in with a paper print out and be fine until the registers.

Still, enough people do stupidly wait until they are in the door threshold and then block the path while digging around, so they should get rid of it.

It’s so that you can’t share your card with friends. You specifically have to live at the same place and have proof when you add them to the account