What good reason is there to remove a headphone jack on a device that isn't even water resistant? There is no good reason whatsoever, unless you wanted to sell more Airpods. Don't you think it's highly likely someone who buys an iPad would also buy Airpods? Airpods are very popular and for a good reason, they work reasonably well and aren't that expensive either (except for the Max but then even these are very decent if you ignore the price tag). Please look around you and tell me how many people use their iPhones with a lightning to headphone jack adapter - zero, that's how many. Nobody does that. People will avoid these for the iPad just like they do on the iPhone - especially when they can get a cheap pair of Airpods 2 for under 100 bucks.
Again, there is no reason to remove headphone jacks. It's not more sustainable, it's not better for the environment. It just makes people buy bluetooth headphones they'll eventually throw out when the battery is flat.
Again, this argument makes zero sense. How can you not get this? Of course it's highly likely that someone who buys an iPad would also buy AirPods, BUT NOT BECAUSE OF A LACK OF A DEDICATE HEADPHONE JACK. Sorry to "yell" but I'm getting tired of repeating myself an apparently it's not sinking in for some of you. I'd say the majority of consumers prefer a wireless audio solution and were already buying AirPods anyway even when there was a headphone jack.
So just pretend for a moment that you're someone who REALLY wants to keep using wired headphones with your new iPad. So you're seriously telling me rather than simply buying a cheap (~$12) pair of USB-C headphones or buying a $9 adapter that you simply keep attached to your headphones, you'd just totally give up on the idea and spend over $100 on AirPods (you're not getting even the older 2nd gen AirPods for under $100 from Apple, that's for sure. You'd be buying used, so that wouldn't benefit Apple anyway). I don't think so.
I guarantee you this is not the reason Apple removed the headphone jack. It would simply make no sense.