Stable coins are not exposed to price volatility like other coins such as Bitcoin and Ethereum. Therefore the price of your stable coin holdings will remain same anytime.

One important use case of stable coins is that you can enjoy to keeping your wealth in the the digital form instead of traditional fiat money in the form of  physical cash without exposing to any change of your wealth. This means, you don't have to keep them in a safe locker or bank or any other physical location.

Another use case of stable coins is that it can be used for trading. In a bear market/trend, value of regular cryptocurrency such as Bitcoin goes down against traditional fiat currency. Therefore, keeping your digital currency in the form of stable coin which is pegged to USD or EUR will help you to not to become unprofitable in a bear market.