Originally Posted by
AKC6
because these tags (pink for DL) are "security
documents."
Which is, in itself, a true statement. These tags indicate whether a bag in the hold has been through TSA security, and thus control whether it can be returned plane-side or not.
However controlling who attaches the tags has zero security benefit, especially when the tags are not removed at the destination.
The part that I'm sure TSA cares about is that no checked bags ever make it onto the plane with a green tag on them - but that would obviously be a function of the checkin/baggage staff, not the gate agents.
The only real reason I can see for forcing them to be attached by a gate agent is that it likely increases the chances they are put on properly (at least for those not familiar with the tags) which potentially reduces the chances of one coming off during loading/unloading, at which point you've got a problem as far as where the bag needs to be delivered.