I'd also be interested in some statistics on the frequency of display damage. With waterproofing and these new types of glasses, I wouldn't be surprised if they had come down rather drastically. I remember every phone I having a cracked display after a year or so. But the last two generations, maybe 5 or six years, they've always survived.
Or maybe it's just my motor skills improving... But if I'm right and they are doing something like 70-80 % fewer display repairs, it becomes really hard to still assume they care very much about that revenue. There are plenty of reasons Apple would want to stop aftermarket parts, mostly of the sort you'll hear if the chef at a fancy restaurant sees the ketchup you brought from home.