The economics, range, and flexibility of a nominal bomb carrier are vastly better than disposable and especially hypersonic delivery platforms. You also have to

The economics, range, and flexibility of a nominal bomb carrier are vastly better than disposable and especially hypersonic delivery platforms. You also have to understand US military doctrine. Platforms like the B-21 are designed to deliver autonomous swarms of stealthy, networked, long-range weapons that can cooperate with each other and adapt to their environment. In this sense, the B-21 is as much a control plane and orchestrator as it is a delivery system. For offensive systems, the US prefers slower, stealthier missiles rather than hypersonic missiles. While hypersonic missiles arrive on target faster, they have serious deficiencies in terms of precision, terminal guidance, range, and payload size. Consequently, the US has had hypersonic missiles for several decades but relegated them almost exclusively to defensive systems where those limitations matter much less because the target is coming to you. This is an option somewhat unique to the US due to their qualitative advantages in stealth and electronic systems, which they lean into heavily. The US 6th generation platforms, like the B-21, are all designed to support unmanned operation, the pilot is optional. In a near peer conflict, communication channels may be severely degraded such that having a person in the seat will have value.