In fairness to AA, this was an IATA standard for decades. I'm sure with the new agent front ends this is changing, but there were literally no apostrophe keys on GDS keyboards, since they were repurposed for other non-standard characters. I still see those keyboards in use in most places, especially where the agents have at least partial access to the native system. Not saying other airlines haven't figured out a better way around it, just saying at least there's a very good backstory on this one.

Back in the dark ages when I was a travel agent, we were trained to drop the apostrophe and skip the space as a standard practice on all bookings with all carriers. Fortunately my state's MVA has the same procedure, so my ID and all my airline accounts all matched.