If you own a device, they reason, you should be able to do anything you want with it.
Copyright infringement and pirated software are big concerns for game companies and those issues have been part of the driving force towards increasingly locked up systems. The PS3, for example, shipped with Linux support which was pulled due to "security concerns."
The Electronic Frontier Foundation (EFF) doesn't think this is fair to the consumer, suggesting that if someone owns a piece of hardware they should be able to do whatever they like with that hardware. The EFF says that this rule doesn't only affect consumers - it's a limiting restriction for indie developers who would create "copyrightable systems and software that would expand the marketplace for these devices and promote the progress of science and the useful arts in these areas."
The EFF seeks to make jailbreaking and otherwise modifying consoles and other devices legal. They say that bypassing restrictions for the purpose of playing homebrew games or add functionality shouldn't be something that console manufacturers can sue over.