And plumping is not badly paid either. But it's a trade that you can learn in relative little time and it's a field that you don't constantly have to readapt your approach. someone who learned plumbing 20 years ago is not outdated. meaning that the supply of people who can fix your pipes is far larger than if it would be similar with IT.
and also there are a lot more people around who have the mental capabilities to learn plumbing than there are people around who are capable of consistently apply the abstract thinking patterns that involve software development.
Recently residents were displaced from their apartments for a month due to persistent flooding in their 5 year old building in Seattle. The manufacturer who developed the novel piping technology claims the plumbing system was incorrectly designed and installed.
I think it's just confusing different terms. I'd say the bulk of programming is similar to plumbing - maintaining, resolving issues, etc. But that software engineering is more similar to engineering in general.
A mechanic works on cars, a mechanical engineer would design the components. Much like IT consultants/administrators would maintain systems and do minor coding, but engineers would deal with architecture and new designs and more advanced solutions to common problems faced by IT.
It's also unfair because plumbers deal with buildings decades old - some even a century. They may have extremely old systems and knowledge of that is important.
Where I live in Los Angeles we recently acquired the USS Iowa, a WWII battleship built in the 1930's. One day I was there, going to the bathroom, and one of the maintenance workers happened to be there and we started chatting. Turns out he was a former SeaBee who was there to retrofit the very old saltwater-based plumbing system to connect to the civilian freshwater system so people could use the head in a normal way. A very non-trivial and specific skillset. If you have ever visited a museum ship you can be sure they had people who knew this stuff.
and also there are a lot more people around who have the mental capabilities to learn plumbing than there are people around who are capable of consistently apply the abstract thinking patterns that involve software development.