It really doesn't, at least not in the US.
There are a bunch of things that are necessary for a contract to be considered enforceable, but the two that are relevant here are "meeting of the minds" and "duress".
"Duress" is the obvious one, but it's a really high bar. It usually means something like physically threatened or blackmailed or literally locked in a room and told you can't leave until you sign. There's not generally a case that an employee or contractor was under duress from their future employer because they always had the option to not take the job in the first place.
"Meeting of the minds" is a bit more subtle. The parties have to believe they're agreeing to the same thing. This is also hard to show, though. Generally speaking, if you've been given the full text of the contract and had ample time to read through it then you are legally considered to know and understand its contents. There are a few cases where shrinkwrap licenses and extremely one sided terms of service get rejected under this theory, but it normally requires the parties to have signed materially different documents or for one party to be able to show that they weren't given adequate access to the document before they signed.
It's also worth noting that contracts are basically considered valid until proven otherwise. So even if there is a case to make that you shouldn't need to comply with some terms of a contract you are bound by you still need the resources (both in terms of relevant supporting documents and in terms of time and money) to actually prove that case in a court of law.