Yes, I believe City-based database file is mandatory. As of DSpace 7 though, I know you can alternatively install the free DBIP city database file instead of the GeoLite one as described here:
https://wiki.lyrasis.org/display/DSDOC7x/SOLR+Statistics#SOLRStatistics-ManagingtheCityDatabaseFile
I would expect that would also work on DSpace 6, but I haven't tried it out.
In any case, the statistics won't work properly without some sort of City Database File, as that file is used to provide the city/country information for all usage statistics.