Plumbers don't get to decide how the pipes were laid out in the houses they come and work in, either - technically those are unknowns that could throw off a job. Doesn't mean it would be professional of them to insinuate that the variation in each individual building means they can't give a good faith estimate for a job.

It means exactly that.

Software industry estimates are way off the mark compared to plumbing industry estimates.

People who don’t like this fact refuse to understand why software isn’t like plumbing.