if you save one potential incursion but in the process antagonise a large number of the rest of your "customers", is that really a success?
Quite frankly, yes. Or would you rather wait for more people to die before it becomes a standard course of action to tag the "remain outside" on the end?
Preventing any potential
Aeromexico disaster is far more important than annoying people who really should just realise it's a safety-first attitude and not be so sensitive about it.
The same reason that at some aerodromes, controllers repeat "hold short runway XX" all the time. Of course when you give a pilot/tug/vehicle a taxi instruction to a holding point before a runway, they're not going to enter the runway.. But experience shows that they do, so you add that on so maybe it will stop that one runway incursion that would have happened otherwise?
It makes perfect sense to me.