I’ve worked on networks for water systems as well and you are right, the problem is people. Weak or default passwords, little to no physical security, it all comes down to the people in charge.
In this side of networking, typically accessibility is considered more important than security as they don’t want to be locked out of something in a pinch. With recent hacks, the opinion is changing, but slowly. The industrial world moves at snails pace compared to the enterprise side. They operate on a if it’s not broke don’t fix mentality.
Same as VGA, shit just works, don’t need to worry about drivers or OS. So if your server shits the bed, you don’t need to worry about these things not working so you can can figure what went wrong.