Does anyone invest in stablecoin? I have never heard although it's possible to get a little profit sometimes. However, people use stablecoin to fix their profit or stop their loss by converting their coin to stable. There's no other use of stablecoin then this.
Honestly I could not get what exactly OP is referring to. It name itself implies about stable then from where we can get "returns"? I guess people are getting misguided by coinmarketcap ranking. Because, coinmarketcap is their Bible and anything at top rank is being wrong interpreted as a safe-heaven opportunity for big ROI. This is the reason why people could not differentiate stable coins from rest of coins and still talking about ROI against stablecoins.