The reason CS researchers do not usually publish their code has nothing to do with dishonesty - nobody is trying to hide their code because it does not really work, or anything like that. It's not even that people are worried of scooping, though that sometimes happens.
The main problem is that any time spent on cleaning up the code, packaging examples, writing instructions, answering bug complaints, etc. is time not spent on things that matter in academia - doing research, presenting it, and teaching students.
It might help if some conferences required source code submissions - but people might just submit to different conferences instead. The only real solution would be if funding agencies like NSF required that any projects funded through them have to release source code. This makes sense from a taxpayer's point of view, and would make the extra work acceptable (since everyone would have to do it).