Stablecoins are generally used:

- by USA government (indirectly) to re-dollarize the world without generating too much USA inflation, another IMF SDR mimicking China usage of foreign currencies to avoid hyperinflation;

- by many migrants in the I world to send money home, something in the III world could be converted to USD at a much cheaper rates and with much simplicity than classic banking/money transfer solutions;

- as a hedge against local currencies, considering dollar or some other currencies much more stable (see for instance the Argentina forcibly conversion overnight of USD accounts to ARS with enormous loss in 2002;

- as a decorrelated asset for DeFi trading on non-stablecoin cryptos (meaning market timing, buying BTC, ETH, SOL, ... when they dip, swapping then to some stablecoins when they top, waiting with the stablecoin for the next dip to buy).

In that regard the (unlikely) real existence of the collateral they claim is not much relevant: as long as most trade on stablecoins come from DeFi the Venezuelans, Bolivians, ... who choose them to bring USD home, the few company using them to pay B2B stakeholders in various countries are still happy anyway, as long as the stablecoin remain de-correlated to other crypto traders are happy anyway.

Tokenised stocks are more likely used to circumvent regulations since you can buy them swapping non-KYC coins against them avoiding capital gains taxes, at least partially.