We may be talking about different things. Executives often negotiate a contract that contains a noncompete. That noncompete has clear consideration as it was negotiated as part of a total deal of employment, theoretically the employee is more highly compensated for this term of the contract. However rank and file employees are often not presented with the noncompete contract until their first day of work after salary negotiations have already taken place and the position accepted. Such an agreement probably isn't enforceable[0] as far as I can read[1] as it's hard to argue its part of the employment contract as the contract is signed after you are already employed and have reported for your first day of work[2]. If it was a employment contract it would've came attached to the offer letter.
[1]"The very basic requirements are that the non-compete must (1) be in writing; (2) be part of an employment contract; (3) be based on valuable consideration; (4) be reasonable in scope of time and of territory; (5) not be against public policy." - https://lincolnderr.com/is-my-non-compete-enforceable/
[2]”One of the most common reasons that courts refuse to enforce Non-Competes is that employers make the mistake of obtaining the agreement from an already-hired employee without providing the employee with anything of value in return. Generally, such agreements are unenforceable because the employee did not receive any additional “consideration.”" - https://macelree.com/the-top-10-mistakes-with-non-competitio...
[0]"Performance of existing duties is not good consideration" - https://en.m.wikipedia.org/wiki/Consideration
[1]"The very basic requirements are that the non-compete must (1) be in writing; (2) be part of an employment contract; (3) be based on valuable consideration; (4) be reasonable in scope of time and of territory; (5) not be against public policy." - https://lincolnderr.com/is-my-non-compete-enforceable/
[2]”One of the most common reasons that courts refuse to enforce Non-Competes is that employers make the mistake of obtaining the agreement from an already-hired employee without providing the employee with anything of value in return. Generally, such agreements are unenforceable because the employee did not receive any additional “consideration.”" - https://macelree.com/the-top-10-mistakes-with-non-competitio...