>>508226562 (OP)Because you're not actually thinking about it.
What's the purpose? To drop a bomb, right? Well why are you dropping the bomb? To destroy something. Why do you want it destroyed? Because it's a threat right now that's why you decided now and not earlier and not later.
What if the bomb doesn't hit? Is that bad? What will happen when they know they've been targeted?
The point of the B2 stealth bomber is to deliver the punch right where it needs to be right now, ideally without ever being spotted, and it's large so it can deliver a lot of punch to ensure the job. And we have several of them just in case.
A "bunch of missiles" can be spotted. Their launch may be known and it is possible to prepare or retreat because information is light speed.
Let's say you're Russia and you have the B2 bombers and the American capitol is in Kansas. Where the fuck are you going to launch "a bunch of missiles" from? The sea obviously, but that's a loooooot of time for them to be shot down.
The stealth bomber flies real high and as far as I'm aware, has never been spotted on a mission.