Generally, courts will uphold a non-compete if there is a protectable interest and the clause is reasonable . Of course they should be banned for low wage earners and in low wage industries.
But in the upper levels non compete clauses for 1 year make a lot of sense in protecting corporate interests. A high level employee working at a consulting firm decides to leave and start their own firm can take the client list. That is not part of a non disclosure agreement which only covers confidential information or proprietary information. But the employee still knows who all the clients are and still knows the cost structure, job process, market insights gianed from training and all other aspects that a non disclosure agreement does not cover. Think of Michael Scott leaving Dunder Mifflin and starting his own paper company. The episode was doen jokingly but that happens quite a bit.
NDA does not stop an employee from taking the names of the clients or taking with them all that training and competitive advantage market info. Client lists are not necessarily proprietary info. Neither is all the training the employee received. In these cases non compete clauses for partners and senior executives are needed to protect the company and the investment they made in the person. NDA's do not cover this.
If an employee is let go, often severance is done in conjunction with non competes.
Non competes for lower level employees, low wage industries or even industries such as restaurants can certainly be struck down as those are ridiculous.
There are also ways around non competes as I have seen lawyers or partners get hired and basically spend the 1 year in an office behind the scenes until their non compete expires.
The 1 year often placed in the agreement is often just a cooling off period to allow the company time to deal with the high level employee leaving and the possible damage they can do. After all an employee that leaves can go to a big client and say "You were paying $600/hour for my work and my team there, I can work for you now on my own for $400/hour and I know your case file very well"