Oh, that old chestnut.
Assuming the whole building isn't covered in security cameras, it takes less than a week for people to just start hitting the emergency door release switches and leaving all the doors unlocked again - especially when you've left your ID card behind and are now trapped in the toilet.
What also tends to happen in some middle manager decides when people should be "allowed" to pass through certain doors based on building opening times etc and comes up with some convoluted schedule of when doors can be used. I have seen:
- Someone get trapped between two sets of doors as he walked through the first set just as the clock hit 8pm and both sets locked themselves shut.
- Rooms get booked for evening use, but someone forgot to "unlock" one set of doors required to get to the room.
- A room get booked for weekend use, but the building locking itself too early (though all internal doors were fine), trapping everyone inside until they walked out a fire escape, activating the fire alarm.
- "Out by 12 hours" errors in the schedule, unlocking buildings overnight.
It's just not worth it and tends not to last long, especially when some manager gets trapped somewhere, or the only way someone can escape is by activating the fire alarm and evacuating the entire building.
Also, the "no tailgating" rule is impossible to enforce pretty much anywhere outside of a secure mental health unit or a prison.