Except that Merchants using Bitcoin still trade in dollars, and must be able to quickly price goods and services in Dollars.
No, people at my side of the ocean trade in Euros. So yeah I'll hack my client to show only Euros, let's teach those Amerifags a lesson!
It makes sense to display the same values for everyone. Otherwise one person would send NN Euros and the other would receive MM Rubels. Based on the current BTC exchange rates of those currencies at some shadowy exchange. No guarantee that you'd actually get that amount of local currency when you're ready to sell, which would confuse the merchant even more than simply regarding it as a foreign currency.
(also, due to internet latency issues, this even applies to two people sending each other $ in BTC. They'd potentially see different exchange rates. Unless the exchange rates would somehow be embedded in the block chain for each instant, this is a recipe for a lot of confusion)
But yes, let's make this an ad hominem attack instead of a practical issue, call me a radical pro-globalist I like that :-)