Makes sense with ISOs. Until you sell the contract or the shares from exercising the options, you don't have any actual money, and those options or shares can go to zero tomorrow (let's say extremely unlikely to happen, but that's not relevant to the point). So there isn't really any actual money to take from you until then.
The second you convert it to actual money by selling, you get hit with taxes (or Nintendo standing behind your shoulder), and you pay off your responsibilities using a chunk of money you've just received.
> Until you sell the contract or the shares from exercising the options, you don't have any actual money
There are other ways of converting them into money, like lending against them. And that is what billionaires are often doing, as it is financially much more attractive. With how things currently are, it would be stupid not to.
That is what I am trying to get across: If we managed to invert the incentives, billionaires might actually sell their stocks, and get taxed on that, rather than finding creative workarounds.
> There are other ways of converting them into money, like lending against them
Isn't that essentially the same as reverse-mortgaging a part of your equity in your house (i.e., borrowing money against a chunk of ownership of your house) to get some liquid cash and then paying that off over time (which would make any income used towards paying off that loan also untaxed)? I was under an assumption that this was something that non-billionaire normal people do as well fairly often (disclaimer: i don't own any property myself, so I am not speaking from my own experience with it).
Of course you need to own a property to make use of that, so that would exclude plenty of people (i.e., non-homeowners), but it can be literally any property you own in any location (from California to Oklahoma to wherever else in the US). And the number of homeowners in the US is significantly larger and is more accessible than just billionaires and other megarich people.
Note: my comment talks about this in the context of the US-only, since that's what the rest of the comment chain is discussing + you can probably write a thick book if you tried answering it comprehensively in the context of all countries in the world.
The second you convert it to actual money by selling, you get hit with taxes (or Nintendo standing behind your shoulder), and you pay off your responsibilities using a chunk of money you've just received.