> here already are some gold pegged stablecoins
Something backed by a volatile asset isn't, by definition, a stablecoin, though.
On a long timescale gold is way more stable than the dollar. Dollar is nonvolatile on a long timescale in the sense the expected returns are negative and it does it reliably at usually anywhere from a return around negative 2-10%. But in terms of price stability gold would be far far far far more stable on anything but the most short-sighted of timescales.
Stable coins are stable relative to their backing asset, not necessarily US dollars or any other currency.