The main reason given is that the article was original research. In other words, it was not just unsourced, but fundamentally unsourceable. There is nowhere an editor can go to reliably determine whether the entries in the list are correct (at least, not to the knowledge of anyone who participated in the deletion discussion). That puts it well outside the bounds of Wikipedia's mission as an encyclopedia, which is a tertiary information source that only summarizes information from other sources.
- Not Comprehensive - Not wholly accurate - Difficult to keep updated - Not all sourced/vergiable or unsourced
Which is totally fair, except that would apply to a lot of articles...