For one, quantum computing may not happen? Like, we're pretty sure it will work, but we aren't actually sure we can make it happen. The closest we've gotten is D-wave and it's still controversial.
The best way to articulate that criticism is to quote me (or at least paraphrase Daniel Lidar) and say:
"We have quantum information processing, but no computers as of yet."
And, that which we already have is so-darned-expensive; that it is less useful than classical computation unless you are building some exotic kind of sensor.
"We have quantum information processing, but no computers as of yet."
And, that which we already have is so-darned-expensive; that it is less useful than classical computation unless you are building some exotic kind of sensor.