It is true that's what 99% of us will see/do. But that doesn't change a basic fact about good engineer - being able to solve "yet unknown/unsolved class of problems" and not just be able to solve "JUST yet unsolved problems". Plumbing is generally about solving "JUST yet unsolved problems" whereas engineering is about the former. Yes, good engineers will also be (will have to be) good plumbers and that's where the 10x thing comes into play in a big way.