Source code really should be available, but it almost never is. The peer review process is, in my opinion, quite flawed. While your paper's high level content gets reviewed, no one actually looks at your code and data to ensure that you didn't forget to carry the one. Your analysis could be totally wrong, but reviewers only review what you say you did, not what you actually did.

Any paper I peer review better have source code available or they will hear about it. That said, yes, there isn't time (or funding) to actually re-run the entire analysis.