Perhaps because you do not do plumbing yourself, you do not realize that making the pipe connections is a trivial part of the job. I learned how to sweat a copper pipe in about 15 minutes of training. You can learn it off YouTube. It is not a high-skilled operation.
I don't know much about plumbing and didn't mean to offend any plumbers but yeah pipe connections definitely seem trivial but I guess that's not most of the job in reality.
I don't think DIYer even bother learning how to sweat copper pipe anymore. I plumbed an entire house myself using pex for the supply. All I had to know was how to press the trigger to expand the pipe.
The only copper I had was a copper stub for the toilet supply, but I used pex expansion to terminate there too because they make copper-pex stubs.
