If they choose to sell it. Whilst markets exist for selling shares in private companies, it’s harder and there is a smaller pool of people looking to buy. On

If they choose to sell it. Whilst markets exist for selling shares in private companies, it’s harder and there is a smaller pool of people looking to buy. On the public market, any shareholder can sell their shares (relatively) easily, and since it’s a public market the pool of potential buyers is much bigger. Employees don’t automatically get money for their shares, being public just makes it easier for them to if they decide they want to.