keep saving iterations of all my old junk.

Backups aren't about saving your old junk. Backup are about saving everything that you have on your hard drive in case it goes to the Great Write-Only Memory In The Sky.

If you're talking about staggered backups or snapshots, their usefulness lies mostly in being a (very primitive) versioning system, as well as a possible lifeline in case your data gets silently corrupted and you don't notice fast enough.