Isn't that effectively what happens though? Barring strong worker's protections (which is not a thing in most of the US) or strong unions (which is not a thing either in most of the US), the only rights an employee gets are "take it or leave it". And that's pretty much what "at will employment" is.

For what it's worth, right to work states that have at will employment also means that a noncompete cannot prevent you from using your skill set to earn a living (aka - you have the "right to work" hence the name). In order for them to be enforceable at all they have to be extremely specific in scope and for a reasonable amount of time, usually only pertaining to not leaving for a direct competitor and taking existing clients with you.

Basically, if you live in an area with a lot of employment options, going to a competitor and trying to take customers with you would be enforceable. If you're in an area without a lot of options for what you do, the noncompete is toilet paper because you can't be prevented from earning a living.

The employee gets any and all rights afforded by local legislation. In most at-will U.S. States, it's almost nothing.

It's 2015. Worker rights have been dead for a decade now, not to imply they were strong at any point before.

We don't have rights via our skills. If you want to have better working conditions, bribe the politicians to make it so (unlikely because you probably aren't paid enough) or organize your fellows into striking until you get better terms (even more unlikely).