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 is because a large percentage of people will be more than likely converting it back to fiat when they need the money. Or it can be so people can see the equivalent price in dollars in case they have never used BTC before