How so?

“Oh no, I made money, better put a small percentage of my gains away for tax season, just like I do with all of my income, because I’m American and lack a good PAYE system”.

There’s a very good reason they should be taxed; half a dozen people are richer than god, and basically never pay any real amount of tax.

“Yes*”

*As with all rules, it can vary by country. As I understand it, the US tends to double tax dividends, which is a rabbit hole of why the US market chases valuation so hard

I think a law stating you can’t borrow against unrealized gains would be sensible.

You can keep your unrealized gains forever, live of your dividends for all i care, and pay no tax. But realizing them, either through selling or borrowing against, triggers a taxation.