Huh? Airline unions have been doing this for years -- nothing new here.

To the OP's concerns, it may be that they have been delayed in other cities, due to weather or maintenance. Yes, there are reserves at hubs but they may not have enough to cover all situations. As for late arriving FA's, usually they are coming from another flight which may have been delayed or arrived at distant gate.

That said, I'm sure many AA crews are not in any hurry to get to their next gate these days. Perhaps when AA merges with US, this will all magically change!