If a professional joins an organisation, creates something novel and valuable, and then is poached to another organisation to do the same thing — that's exactly what patents are there to protect.

Say they spend 5 years developing a nice kind of lubricant — the company can patent that lubricant. Then if the professional goes and joins another company, even if they have that knowledge, they'd have to conduct new research to find a new approach which doesn't run afoul of the existing patent. That's the point — patent's don't protect your market dominance, they just protect against imitation/copying.

Now say the work of that professional is systems architecture for some Google project, and they leave and join Facebook to build the same systems architecture for Facebook's project — of course that shouldn't be patented (although sometimes it is, and that's a different issue.)

A "restraint of trade" agreement in your employment contract (a "non-compete") is intended protect companies from others copying their product when other IP rights don't exist — and I agree that it shouldn't exist. It quite literally prevents new invention and done through an imbalance of power. But, organisational already have plenty of mechanisms to mitigate that risk — pay the person more, better working conditions, or just pay them a long gardening period.