On the other hand we now have waterless urinals. Maybe plumbing tech and equipment costs have eliminated some jobs and made some jobs less skilled as it cheaper

On the other hand we now have waterless urinals. Maybe plumbing tech and equipment costs have eliminated some jobs and made some jobs less skilled as it cheaper just to replace than do repairs that take knowledge. Software jobs are many X what they were 30 years ago, while I doubt plumbing jobs have change that much above what they were relative to the population 30 years ago.