Because that server isn't in the cloud. It's on leased hardware, so no ability to snapshot. Plus, I like it when I can replicate my data without worry. I don't want to have to rely on block-level replication.
base698 isn't saying take a snapshot of the server, he's saying take a snapshot of the DB; find the directory it is stored in and `cp` that.
That's not a good snapshot unless you're running LVM or can afford to suspend writes and fsync + lock.
And again, this is yet another problem solved decades ago by RDBMSs.