It depends on the conference or journal they submit to. I typically request that authors release data and code in the review and the same is requested of me when I submit a paper for review. I don't know, maybe CHI doesn't have that sort of culture. Or maybe they do and these students just don't have the time right now and plan to do it right before the conference in May.
Indeed, there is no culture of replicability at CHI (and even less so at UIST). Reviewers usually reward novelty and cool PoC videos, not thoroughness. It is quite rare (especially for U.S. labs) to also publish source code, schematics, or raw data. There have been some initiatives advocating for replicability, and some researchers indeed publish everything, but in the whole, a quick, shiny video of a PoC implementation is often sufficient for a paper to be accepted.
