It depends on the route. Last month, I was surprised to find that my scheduled 9:10p departure from JFK to SAN had a full dinner. That flight ended up being delayed, so dinner was served well after 10pm.

I appreciated having food on this ~6 hr flight, because, while it was a late departure, I never seem to have time for dinner before my flights when I'm in NYC -- too many other things to do, and getting to JFK is always a mess, especially from Manhattan.

You'll find that some transcon flights like this will have late dinners. However, for most domestic flights, AA will stick to the pre-8pm rule.