I think that it's likely because Apple has much more leverage and their major source of funding isn't their browser. I could imagine a world where ad-based services started blocking/paywalling Firefox user-agents. Hopefully now that Apple has opened the door Mozilla is safe to walk through too.
Publishers are already treating adblock (not tracking protection) users far more aggressively than they have in the past. I imagine if the number of users that are hampering advertiser value went up by an order of magnitude that these publishers may react in a far more aggressive way.
That depends, really. Firefox usage is barely in the double digits and has been steadily declining for quite a while. If it becomes a hassle, then maybe. I'd expect them to boot Safari users first. We will have to see how it goes.
