OK, let's run with that analogy.
What if that same manufacturer was the one who made the tires; you can't buy the car with any other brand. In fact, those tires can't ever be completely removed. And suppose that it was well known that those tires were defective, making it easier for theives to steal your car, and that they had sent you numerous patches for them to get you by, and that other defective parts, including the tires, had always been patched and upgraded for free in the past. Owners of these vehicles are expecting the manufacturer to eventually fix the problems with these tires and send out new ones; they had done so before.
Lets suppose that your company owned thousands of these vehicles, and that they only had about 30-40,000 miles on each of them. They still have plenty of good use left. Now, the new tires are finally announced, they're finally going to be released! But, the manufacturer announces that they are only going to make the new tires for their newest model. One model.
You, and others like you, will just have to live with the defective, unsecure tires they gave you for free as an enhancement to the more defective and more unsecure tires the car came with originally.
...or, and this is the likely result, more and more Windows users are going to be switching to the much more secure Firefox-branded tires. :-)
Excellent response.