Serious question: Why? I've never found it particularly helpful myself, but what's the big deal about a sound that reminds you to put on a critical safety device that you should already be using anyway? Do you really find yourself hearing those dings for long enough that it becomes a serious annoyance? If so, don't you think the ding isn't the actual problem there?
Also, the promise of market economy is that, under competitive pressure, in time product's price drops to near the actual costs of making it. Some products are simply done, and there should be a point at which the profit from sales is enough to just keep making it indefinitely, and the company could be free to pursue other products in other areas while still making the old one.
What wasn't the advertised part of the bargain is the ratchet effect - a company will add user-hostile feature, briefly get a better deal, then all other competitors will follow suit and suddenly the user-friendly product is no longer being made. We need to develop a way to prevent this.