Ethos ran on ETH vouching for over a year, and it worked. So why a native token? Because four properties of the network can't be achieved any other way.
Alignment
The people who build the credibility graph own the asset tied to it. With ETH or USDC, contributors do free work for infrastructure they hold no stake in. With $WHUF, every contributor is an owner — the network is constituted by their staked conviction, and they hold the asset that reflects its health.
Incentives
The 18% contributor rewards pool pays vouchers perpetually, from a fixed allocation committed at genesis. Try that in USDC: someone must fund it with real dollars, forever, which forces a revenue model onto the protocol. A native token pays builders in ownership of the thing they're building.
Self-sufficiency
Fees are burned, not collected. You can't burn USDC — destroying it just donates to its issuer — so a stablecoin fee must be collected by someone, and every candidate for "someone" turns the protocol into a business. With a native asset, the economic layer has no income and no expenses. Nothing to collect, nothing to corrupt.
They compound
Rewards draw tokens into vouches; vouches deepen the graph; a credible graph attracts usage; usage burns supply and deters spam; contributors accumulate ownership. Each mechanism feeds the next with no external subsidy — a loop a borrowed asset structurally cannot close.