I don't think it's necessarily just people trying to appear smart to their peers and creating abstractions to do so. I think it's an intermediate programmer problem that comes from seeing their own novice programmer code spiral out of control from sprawling redundancy. It comes from one too many meetings where someone says something like "can't you just change the website so that all the red links and controls are now blue", and kicking oneself in hindsight for not somehow tying it all together. And I think it culminates in programmers thinking that if only they'd made it with some kind of unified but flexible abstraction it wouldn't have been a problem.

So when it comes time to write the next app that "unified but flexible" becomes the mantra, and yes it is fun at the early stages of a project to fantasize about permutations and invent great abstraction towers to cover these cases. But I think the problem that people have is that they don't respect that flexibility comes in infinite dimensions, and that you can only pick and choose a few specific dimensions of flexibility to cover. Not only that, but each unnecessary dimension of flexibility added makes the code significantly longer and more complicated and just generally difficult to reason with. In hindsight from the previous project it all seemed obvious which dimensions should have been flexible, but making that call correctly up front is incredibly difficult.