because synching runs all the time. any change that I make is nearly immediately updated offsite. and if you think that is my only backup of my photos, you would be wrong :-) This is only a “if I lost all my physical possessions” type backup, not an “oops, I am a dummy and deleted something I shouldn’t have” backup. I have multiple snapshot backups and also run incremental backups every hour. Storage is so cheap any more that I don’t hesitate to have 5 backups of the REALLY important stuff. Most of my server storage is also raid5 in case of hardware failure. I have pushover set up to check for disk failures and push alerts to my phone if one is ever detected.