Benefits of oil change are also invisible until it’s too late, yet no one has problems understanding it. Can we learn something from that field, maybe? I’m grasping at straws here.
Software can limp along broken without anyone noticing for far longer.
Directly measured, the engine cylinder walls will grow wider and compression will be lost. Indirectly we can do an oil analysis and see the metals deposited.
One of the reasons we do not understand the cost of low internal quality code is that we do not know the "spec". Defect rates is one proxy measurement, but it's hard to know if it's just "bad programming" or "bad internal code quality" ...
no, it's because the engine will seize and fail if you don't change the oil, and it's readily apparent to everyone when it happens.