I'm not sure if this is entirely a budget issue, or stereotypical Amercian arrogance. NASA choosing to keep imperial measurements on some projects, even current ones, is a recipe for disaster.
Before you go flaming me for the "arrogant American" comment, it's a sterotype... I am well aware that the majority of American's do not fit in this mold. It is, however, a sterotype widely recognised throughout the world.
So, is this an example of said arrogance? Is this purely a financial constraint? I'd have to believe the truth lies somewhere in the middle. While the rest of the world, including much of the US, uses the Metric system in all things scientific, this just seems... dumb.
NASA's own Mars Climate Orbiter burned up on entry into Mars' atmosphere due to calculation errors between imperial and Metric. Following this incident, NASA reverted back to using Imperial units as their only system of measurement, starting with the Mars Rovers in 2004.
If the US, or NASA, were the only agencies working in space I would see few problems arrising. Not a smart decision, but it shouldn't have any negative results. However, there are currently 15 other countries involved in the International Space Station alone - all of which use the Metric system.
Wait for it... disaster will happen. The aviation world learned a valuable lesson which impacted the entire commercial airline industry. Let's hope NASA doesn't learn the hard way.