It's not buying a cup of coffee that's the issue. The issue is in converting between currencies, which is no different than investing in foreign currencies. If you exchange USD for EUR, wait a while, then exchange back to USD and you've made a profit, it's taxable.
Every taxable event is something you have to keep track of.
And spending appreciated crypto, even on coffee, or anything else, is a taxable event.
So the point stands that using crypto as "spending money" vs purposefully saving it as store of value is going to be a real pain, for all of the technical reasons but also the tax complexity.
To see why this is the case, imagine someone saved BTC as store of value, then years later exchanged it for a house.
They didn't sell if for $. But they used its appreciated value to buy something. There is a capital gain involved, and so taxes as well.
It is, though. Transacting with bitcoin is a taxable event just like converting between bitcoin and fiat. It's no different from the IRS's perspective.
