I understand where you are coming from. Once someone earns their shares and becomes vested those shares are essentially unavailable. Whether that vested equity holder moves on or stays is inconsequential. Each vested person has earned their shares. Whatever work the remaining shareholders and employees put in is for their equity to grow.

It’s like building a house with someone and one person leaves but still has equity. The person that continues to live in it renovates and maintains it selling it for much more several years later. The equity holder that left still gets half. That’s the way it is.