[gozur88]

I locked myself out of the house one day and called a locksmith. It took him less than thirty seconds to pick the lock on my front door.

You're right about the signaling aspect, though. You can't very well pretend you didn't know you were supposed to be in a room if you had to get past a locked door to get in.

[closeparen]

Except when organizations decide it would be too much of a security risk to give every authorized person keys/cards, or doesn't do so in a timely manner. Then the one designated key-holder is too busy/important to personally let everyone in, so the "secure" door gets propped open and/or opened in response to a knock from anyone, authorized or not. When low-level but authorized staff need access to further secure spaces, they start by tracking down someone with higher access privileges to borrow a card from. People with high-privileged access then start to reflexively toss their credentials to anyone who asks, because most of the time the request is necessary.

Super common with event venues during rehearsals and preparation (below the level of production value where there's a security desk checking IDs).

[RyJones]

My locksmith didn't pick my lock. He asked if I wanted a show of lock picking or my door open. I said open. He turned the doorknob, held it on the stop, leaned on the door, slid in a thin plastic shim, and turned the doorknob the rest of the way.

Impressive!