When you are looking for “random items” in the "Reasonator", you want to see items that are of interest. For all kinds of reasons, Wikidata includes references to templates, categories, disambiguation pages and list articles.
They do not have much to offer that is of a random interest.
For this reason are all such items filtered from the random results. Sadly many categories, templates, disambiguation pages and list articles are not marked as such. As it does not take much effort to add the relevant statements, we hope that in the future you will see them not as much as you will today.