My experience has been that most of the time, NCAs are almost completely onesided to the company.
I was attempting to transition from being a W-2 employee to a subcontractor at one company. They gave me a copy of the agreement to review, which I took to an attorney because it was so onesided. We revised it to be more fair to all parties and sent the agreement back. A couple days later the company returned a copy of the revised agreement with literally ALL
of our revisions marked out and reverted back to the original agreement. Oh, and at that point they wanted to "start" the negotiations. It only cost me $1500
Thankfully, their HR staff wasn't entirely on the ball when they hired me and did not have a NCA on file for me. Needless to say, I didn't remain with that company.
While this isn't exactly the same scenario, it falls in line with most of the NCAs I have read - the company would rather you take all the risk...