Militarily, it's the lowest-flying and the most maneuverable spy satellite with a turning radius comparable to the size of an European mini/microstate. That's it.

Just speaking from a couch, maybe it's a simple 50:50 between the NASA administrator just wanting it flying and Boom Supersonic not doing fantastically. Anduril's mini F-16 drone having its air intake painted out in photos also comes to mind. Lessons learned by NASA from an SR-71 engine project is going to be invaluable for new entrants to supersonic planes and engines.

The only thing it was designed for: recon. It's a spy plane. It has cameras and electronics up the wazoo. You fly it high and fast over a target, collect the info you need, refuel it and change target. Unlike a satellite, you can do that many times per day.

Against the USSR it had become risky because missiles could reach it? And satellites worked great during the cold war. But in a scenario where things got hotter and you wanted regular fresh intel from deep within enemy territory, the SR-71 could be irreplaceable.