A depeg is a market verdict on backing. Small deviations of a few basis points are normal friction; a sustained move of 1% or more says traders doubt they can redeem at par, or that the exit is too crowded to try.
Depegs matter far beyond the token itself. Lending protocols price collateral through an oracle, so a stablecoin printing $0.90 can trigger mass on-chain-liquidation of positions that were never insolvent in economic terms. Pegged wrappers and liquid-staking receipts can depeg for a different reason: the redemption queue is long, so the discount is a time value, not a solvency signal.
Trading depegs looks attractive and is asymmetric. Buying at $0.95 for a $1 redemption caps the upside at about 5% while the downside is the whole position if the backing is genuinely impaired. Anyone doing it is effectively writing insurance on an issuer's solvency.
Related: stablecoin, fiat-backed-stablecoin, algorithmic-stablecoin, stablecoin-redemption