That's what I'm saying. Vacuum tubes had various evacuated tubes as their precursors which had uses in experimentation and industrial applications. This led to a step by step development process with continuous subsequent innovations building on each other. Quantum computing on the other hand is kind of an all or nothing proposition with many problems that must be solved which only produce value when functioning as part of the whole.

I don't think the development of classical computing is a good analogy either as the shared memory computer had various electromechanical precursors that had utility all of their own.