Very true, they have different uses. The real purpose of the 71 was to penetrate the Soviet Unions airspace at high altitude (80,000-100,000ft), and very high speeds(Mach 3.5+) and take pictures of what they were doing.

However, in a warzone, like Iraq, where they do not have extensive military aicraft and SAMs to shoot the U-2 down, the 71 would be a waste of money. Plus we'd probably piss Iran or some other country off for flying over their country, even if it was only for a few minutes.