Why not make a law against using unrealized capital gains as loan collateral?
Because that would outlaw home equity loans, for one thing. Anything you own that’s increased in value since you started owning it is “unrealized capital gains” by definition, until/unless you sell it, not just stocks.
The fact is, taking a loan out using stuff you own as collateral, regardless of what it is, is a perfectly normal thing to do that in itself deprives no one of anything. Lenders aren’t in the business of throwing money out the window—they make these loans because they get repaid, and then some. Someone who takes out a home equity loan and uses the money to renovate their house so that it’ll sell for an increased price beyond the loan amount + the interest rate, is making the exact same ‘move’ as someone who takes a loan out using their stock in a company as collateral, and uses that money to do things that make that stock increase in value beyond the loan amount + the interest rate.


It’s not a “fairness argument”. I’m not arguing some subjective value judgment of mine, to be debated.
If you expect your roulette bet to pay out when you win, you’d better believe it’s part of the arrangement that the casino is not going to give your bet back when you lose. You can’t get the payout without the risk of loss; similarly, that’s how owning stock works.
So if you as a worker want the benefit that comes with your employer’s company’s net worth going up (which many workers do in fact get, it’s not that rare for stock to be part of a compensation package), it is only fair that you also accept the possibility of being on the hook if it goes down (which is what happens if you’re paid in stock whose price goes down after you receive it).
You can’t have it both ways.