Your comparisons are a little silly, too. There are good reasons (right of way, regulation) and bad (monopoly concessions, lobbying, corruption) that private utilities own entire markets. These have nothing to do with the forces behind noncompetes. No noncompete has helped establish any company's monopoly in any product or service you can name, even regionally.
Noncompetes are a trade. Companies provide employees with access to resources, client lists, and trade secrets. They want to ensure that rolodexes aren't shopped and product plans aren't bootlegged. These are reasonable goals. Employment contracts are blunt and inefficient instruments for accomplishing those goals, but that doesn't make the intent corrupt.