For Bitcoins, concerns about trust are warranted. Currency requires trust that it retains value; that is not given for Bitcoin and its countless clones at all.
Stablecoins collateralised by actual dollars quite obviously require trust, namely in the entity providing and holding the collateral.
Stablecoins collateralised by "the algorithm" have never been seriously tested, in my opinion, and it not clear to me at all whether you can manufacture stability algorithmically. DAI, SAI, MAI, whatever, are only collateralised by "assets" on the Ethereum blockchain, so ultimately self-referential (or, if collateralised by something tied to something real, require trust there.)
https://crypto-anonymous-2021.medium.com/the-bit-short-insid...
DAI specifically is collateralized with ETH using smart contracts - it's over 100% collateralization is incontrovertible.
So effectively, you've linked DAI to the value of a coin that is set by tether. That being the case, the actual value of the collateral is in question.
That's why I replied that way.
On the topic of price fluctuations, I'd like to point out that not only are there a plurality of stablecoins pegged against and collateralized with dollars, there are also synthetic assets like DAI which follow in Satoshi's footsteps - using game theory, economics, and finance, to novel and practical effect.
I highly recommend reading the Bitcoin, Ethereum, and DAI whitepapers (in that order).
https://bitcoin.org/bitcoin.pdf
https://ethereum.org/en/whitepaper/
https://makerdao.com/en/whitepaper/