This technology would be very valuable to whoever creates it, and its value would decrease if it were to be known to exist.
We can't think only in terms of profit-based incentives. Some adversaries -- like nation states or a consortium thereof -- could permanently destroy faith in Bitcoin by releasing this sort of quantum computer in the wild. That may be incentive enough.
Yeah first person to be able to crack keys 🔑 in a reasonable time will not want to do so in a blatant way.
Just a piece here or there.
You're thinking like a thief, not an adversary who wants to destroy Bitcoin. We should plan for both scenarios.