A missile isn't generally reusable - they're designed to operate at a region of performance within their engines that would not even allow for sustained flight.

A missile isn't generally reusable - they're designed to operate at a region of performance within their engines that would not even allow for sustained flight. If it only has to "live" for a few minutes, you can get a LOT more performance out of it, which is exactly what they're designed around. But it's a trade-off. You could invest in a (practically) infinite supply of global capable missiles to be launched from the literal center of America, and to get 24 hour coverage you just launch one every 30 minutes. But that's extremely expensive and stupid. But a missile which is carried to be closer to the battle can be smaller, and cheaper. Then you need some kind of vehicle to get it there. This kind of thing is that vehicle.