Simple, it’s progressive, so if you are very wealthy and own 30% of the company you might need to sell 5% to pay off wealth taxes over a few years, and you sell them to people or institutions, with less wealth (and therefore less wealth taxes due). It wouldn’t end up with the government owning the shares, it would end up with people at a tax advantage relative to you owning the shares.

Whether or not that is a good idea, I don’t know.