[judge2020]

Common law of contracts dictates that you can commit to performing certain services in exchange for the counter-party performing certain services. For example, you provide both money, viewing data, and permission to run DRM and proprietary code on your property (e.g. set-top boxes or smart TVs) to Netflix in exchange for obtaining access to their library of TV shows and movies.

It's codified in the fact that saying you'll do something means you're socially obligated to do it, and legally obligated if you receive something in return.

[tedivm]

You still haven't said where it's legal that all rights can be signed away. I know for a fact that you can't waive tenant rights when signing a lease, for example. We also don't allow people to sign over so many rights that they're considered slaves, as slavery has been made illegal. I also can't sign away my right to not be sexually harassed- if a company makes me sign something saying that they can sexually harass me they will still end up losing in court. The US has also limited the ability for NDAs to cover discussions about labor practices, so there's another right we can't sign away.

It seems to me there are a to of counter examples to this "right" you speak of. So many that it doesn't seem like it really exists.