That is probably true, however, I personally use it to share with others who are not part of my network, calendar integration, password database access across many devices, rsync backups across *many devices, document editing via Collabora and probably other things I'm not thinking about at the moment. I don't have the performance issues that others note, but I took all of the performance improvement steps noted in the documentation: have bare metal well-resourced db hosts (for multiple services), dedicated redis cache, properly configured php-fpm, etc.