“When an investor focuses on short-term investments; he or she is observing the variability of the portfolio, not the returns – in short, being fooled by randomness.” – Nassim Nicholas Taleb.
Therefore stablecoins, like most cryptocurrencies are a purely speculative asset. Stablecoin speculators bet that these assets will work as advertised. If stablecoins fail the speculators will lose their money.
Thus, stablecoins are an inherently risky asset based on unproven technologies and business models. Thus only people who can afford to lose money should buy stablecoins.