I sometimes wonder if programmers instinctively overcomplicate things in interest of collective job security. Some of the stuff I've seen in (particularly awful) Java code bases is perplexing to the point where it seems intentional.
I could talk about people unprepared for the jobs they do, and companies and managers setting unrealistic deadlines, having unrealistic expectations, etc. But I think most often than not, the issue is that to really build good code, you need to have a lot of experience and plan and design really well from the start. And simply, most companies and products start as they can. If you start with a deficient codebase, trying to fix that later under heavy budget and time constraints is pretty much impossible, and it's so accepted that some people believe it's the normal way to work.
And even with proper design, clear perspective, and good programmers, you still have to be lucky that no one higher up the ladder imposes decisions that f*ck up all the good work done. There are a few factors more.
What I mean is that you might find all kinds of people, but in general, for those of us who care about what we are doing it's the exact opposite. We consciously try really hard to keep code as simple as possible.
It’s more likely boredom. Cranking out yet another CRUD app is more fun if you do it in a weird way. And a new “skill” for your resume.