It's the other way around. I have no requirements that need it to have a normal database.

The biggest two advantages of not having a database are simplicity (I don't have to query the database to access the data, as it's already in memory) and speed (my average response times are well under 1ms, and that is with compressing every reply, having more data in memory than I have RAM, running on a cheap dual core VPS, and being flooded with requests from linking to my site on HN).