That's the right description about stable coins but it's not that many of them at all. There are actually a few of them that are popular.
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.
Probably a newbie that doesn't understand it if he/she buys it, they will be think that they have invested on cryptocurrencies.