From the linked benchmark:

In RethinDB, you have to create databases and tables manually and it will raise an exception if they already exist. Compared to MongoDB that could be an inconvenience for some(and me) - one of the things I find appealing in MongoDB is the fluid interaction with databases

... well at least now I don't feel so bad about having some old MySQL stuff still in production. MySQL already has too much "fluidity" in dealing with my data...