Backing up an SQLite database is as simple as copying a single file. As long as nothing is writing in the file, you're good.

That's not a reason.

Plus setting up a nightly back up of any SQL database, regardless of creed, is like a 10 line cron job.

Some developers have never written a cron job.

I think the point here is, SQLite setup would provide satisfactory results at this scale.

If the choice is betweeen a PAAS database offering and SQLite, you can pick SQLite. If you have skills / are prepared for managing dbserver yourself, then do that.