[yakult]

It's not that simple. What if some of it is proprietary? What if I'm not allowed to submit code because I need to be anonymous so reviewers can maintain impartiality? What happens when one of the upstreams update and breaks my code? Do I need to keep it updated? Forever?

[adrianN]

At my institute at least, scientists are required to maintain everything that is necessary to reproduce a result for at least ten years. That includes all the data and the software used to produce the results. It's not an easy job, but it's important.

[yakult]

If your institute also mandates they make the data/software publicly available, then that's definitely the exception rather than rule. Also must be hideously expensive.

It almost never happens that a paper I read actually comes with usable source code.

[pixl97]

Then your results are not reproducible and your conclusion is suspect.