Hoarding has the goal of delayed buying. Of course, some people can hoard for the sake of hoarding, but most do it to store value for purposes of future consumption. Which again brings us to unique consumption cases that this or that currency can provide.
Once the expected loss in transaction costs is smaller than the expected loss of the transactional currency being a weaker store of value, people prefer currency exchange to hoarding the transactional currency. Between cryptos, currency exchange cost is very low, so I don't give much chance of success to a coin that is a weak store of value even though it had superlative transactional use.
But higher usage on the other hand makes a coin gain in value also, therefore making it a better store of value.
I see you have a somewhat balanced view on what you call transactional currencies, which is good compared to those who don't bother to check or think about advantages and disadvantages. I have one question though. When you say people exchange from transactional currencies to another, which supposedly is a better store of value, do you mean crypto, Bitcoin? If you mean crypto, how do you consider it a good store of value with hundreds of percentage points in yearly fluctuations? It makes it no better than a transactional currency. I think it's too premature to call any crypto a good store of value, as there is no history of stability supporting this theory. And once we have no good store of value among cryptos, we're back to transactional currencies.