When Krusader users utilize the "Search for" comboBox on the "Locate" dialog: they often see bad entries because there are obsolete ones, mistakes and so on, but normal Krusader users can't remove those entries. For example, web browsers have Shift+Del in order to remove the thwarting entries.
With a KrHistoryComboBox, Krusader users are able to delete wrong entries from history lists, and therefore they can remove those bad suggestions that they were seeing.