I suspect that's also why some papers are unnecesarely verbose and describe simple things as complicated as possible. Can't criticize something that can't be understood.
Hiding code, obfuscating language, fudging data, all are symptoms of the same problem: of being interested in getting paper on cv instead of doing research.
There are many circumstances that can put even a good scientist in a situation where he/she has to do this but that's not a good argument for not sharing the code.
I also detest simple things made complex, though. In my experience (with has covered electronics, epidemiology and geography) reviewers tend to pick up on obtuse issues in text but miss glaring errors in the math. It's sad, and you can see why someone less than scrupulous would exploit that tendency by over complicating things. That said I think plenty of authors are honest but just not very clear thinkers!