Dollars only have hypothetical value until spent as well, but we still tax them.

I'm not super rich but if the government wanted to tax my shares, I'd pay the tax out of my income instead of buying more shares. I could probably pay a decent chunk of it out of dividends too, if I wasn't reinventing them.

Property tax here in Australia is based on hypothetical value, the sky doesn't fall.

Even if people have to sell some shares, I just don't care, it's not a big deal. Sell em.