> The price volatility seems like a red herring. If you're using it as a currency then you're not holding it for significant periods of time and the entire point is to make it an automated process, so you're buying some cryptocurrency for cash and then immediately spending it. How much volatility do you really expect in the timespan of a fraction of a second?

Maybe I don't understand how people use bitcoin but I wouldn't call your description that of a currency but more like a payment processor.

I want a currency, e.g. USD to be stable enough that I can comparison shop in it, quote prices to customers in it, and hold some as "cash or cash equivalents" on my balance sheet without undue risk from price fluctuation.

USD achieves this, BTC doesn't, which is assume is why people are using the get-in-get-out model being mentioned here of only holding it for as short as possible.