"Wouldn't it have been cheaper and easier to have fitted the U2 with a nose-mounted video camera and some sort of "parking sensor" arrangement for the last few feet?
Or how about a Concorde droop-snoot?"
You have to remember the plane was designed over 50 years ago! As to a drooping nose, it doesn't sit that high off the ground so there isn't much room to droop. Plus the goal was to make the plane as light as possible. Every pound saved was worth some number of feet higher ceiling. Kelly carried this to an extreme when he designed the SR-71 with external starters.