Combine unrealized capital gain taxes with fiat system, and you get an incredible wealth transfer weapon towards the rich, paradoxically supported by socialists that are clueless on what's actually going on.
For example, in France, unrealized capital gains can get taxed during a succession. The original intention was to prevent golden-spoon-fed children to just inherit the wealth of their parent too easily.
The result is killing family owned businesses and farms. Farmers that inherit land or a business do not have the liquidity to pay the tax on the accrued value of their land or equity. At best, you take on debt with your business as colateral, gifting a slice of your revenue to finance bros, at worse, you are forced to sell to cantillionnaires, further accelerating inequalities the law was supposed to fight.
Unrealized capital gain taxes essentially forces everyone that doesn't have deep liquidity to sell at a steep discount their assets to the few that have access to cheap debt.
It's a trojan horse.