As far as I experienced, research is the most important factor for promotion, as it represents different features of an academician/scholar, which are needed by higher education institutions: teaching at graduate level, supervising academic projects of graduate students, attracting research fund, fame for the university, etc.
Publications is normally the main measure for research of a professor. Thus, one expects to see a proportional relationship between publications (both quality and quantity) and academic rank.
People can be promoted with less publications, probably because of other activities. But, I wonder why there are some academicians whose rank is far behind their publications. For example, I have seen people with 50 papers but are still assistant professor, or over 100 papers but still associate professor. I am referring to the US universities.
What keeps an assistant/associate professor with a strong publication record from appropriate promotion?