I've seen loads of topics of people trying to sell things and saying I want x amount of dollars worth of BTC. Surely if someone is so keen on the idea of Bitcoin fiat shouldn't even be mentioned.
They should be prepared in certain instances to take a fiat loss for their beliefs.
it's not as simple as you think. bitcoin's price is always rising, so .02 btc is not the same today as it is tomorrow. plus, fiat is our point of reference, since bitcoins are denominated into decimals. it's hard to scale them.