Sure, I should have maybe made my point clearer and say PLC programmers in my experience are often guys with no programming background who have an Associates in automation technology or something similar from a local community college.

They have often not been taught basic things like don't name a variables or identifiers that have no significance like 'b123' and are in a workplace where as long as the lines are running properly nobody cares. There are leagues of difference between what I would consider a pretty messy codebase at say, some B2B enterprise software company, and a large codebase maintained by people who actively don't know how to program for lack of a better description.