Well you do have a point. Owning stable coins is like owning traditional fiat and it has almost no added value cumulatively since volatility is very low. But still, that doesn't mean they are good for nothing. Stable coins can be used to escape the effects of volatility when necessary. That for example means if I wish to spend $X amount of a coin say bitcoin for example in a couple of weeks and I feel there may be price shifts which I'm not willing to risk , ill just swap a couple sats to USDT to save me the stress of unnecessary calculations.
There are numerous examples including cases where certain things must be priced in fiat especially dollar and you have the risk of dynamic rates leading to price alterations too.
You can refer to USDe with an APR of up to 29% per year. Of course, in an uptrend, investors are attracted by the profits from the strong price increase of the token, but in a downtrend, things will change when investors want to hold USDe to earn profits while waiting for the market to recover.
Although USDe has rewards from ETH staking, I still have a feeling that it's similar to UST that Terra used to issue. I believe USDe will be favored by companies in the DeFi sector because they manage huge amounts of customer money and need a safe project with an attractive APR like USDe. Then we will have to face the risk that USDe cannot provide a high APR as it is now, and many DeFi companies will go bankrupt, dragging the market into the next crypto winter @@