A truly dedicated thief won't be deterred by limited access points. There's always an element of sociopathy in these people, so they won't think twice about doing something like pulling a fire alarm when they're ready to make off with the loot, so that everybody in the building has to get out fast without being scanned.

It doesn't matter at all to them that they've inconvenienced hundreds or even thousands of people in their determination to get what they want, and that is precisely the weakness they exploit in the standard physical security playbook.