For backup.
So all of my hard drives and devices are in the same house, if I was sleeping and and house caught on fire and I couldn't even get my phone in time (just a worst case example), then I lose all my passwords.
Cloud is my "offsite backup". Cuz where else would I put stuff?
Also: I though you could just safely upload encrypted files to Google Drive, why not a password database? It's just another encrypted file.