[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.