Not so simple. Let me illustrate in increasing levels of absurdity: if Peach Inc. tried to, say, claim property of any data or content authored, produced or processed with any of their devices, and forbid you from using them in the loo because it damages their image, and claims rights on the organs of your firstborn child when you open some DVD shrink wrap, etc. etc. and I find that aberrant, there is a point at which "so don't use Peach hardware" doesn't settle the issue.

For many people, being forbidden to use a piece of hardware that you legally own in whatever way you want is an unacceptable intrusion on personal freedom.

"For many people, being forbidden to use a piece of hardware that you legally own in whatever way you want is an unacceptable intrusion on personal freedom." So don't buy hardware with those restrictions! For all the acknowledged absurdity of your opening (there are laws that exist to prevent that sort of thing), the fundamental fact of the matter is that as a consumer, you are free to choose not to buy something. If the market doesn't offer what you want you have two options; the obvious one is to do without. The other option is to develop your own.

My point is, why are there laws that exist to prevent the sort of absurd things I propose? That is, why isn't "if you don't like it then don't buy it" sufficient in those cases?

There is a line to be drawn somewhere and different people may reasonably argue for drawing it at different places.

As the recent jailbreak exception shows, you are not legally forbidden from doing anything you want with the device you own.