The only time I see non-competes as reasonable is when someone sells a business. It seems fair to put a territory restriction on a seller so the new owner doesn't have to immediately start competing against the person they bought out.
Why? They started one successful business. It seems good for society if they go on to start another.
Noncompete shouldn’t be so broad that I couldn’t move to another city and start a lawn care business there, but I shouldn’t be able to compete directly with the business I just sold using my insider information of that business.