Sure, but almost no-one flies brand new airplanes. What percentage of GA flights do you guess contain an AoA display? And the argument's supposed to be that they're a most important indicator for airplanes?
Note that many light aircraft have stall warning horns, which are just AoA sensors that only detect when the AoA exceeds a certain amount. In many other planes, you can detect excessive AoA by sound or feel.
Pretty difficult argument to make when most planes do not have AoA sensors!