They are a better currency than an investment
(store of value, unit of account, medium of exchange)

They don't pay interest or anything.  They are what they are.

But as they say, "bad money drives out good".
This means that good money goes into hiding in wallets, storage, while bad money gets exchanged for stuff.
When you can trade bad money for good money, you do it.
So your question is really, is it better money than the alternatives.
In some ways yes, in others no.  If it is better for you, than hold it, and trade away your fiat currencies.