Actually, I think that one at least has some history to it.

The disk drive was one of the first ways to store information between computer sessions as the first computers didn't have built in storage. You would create a program, run it, and then when you shut the computer off it was gone. Since the disk drive was used to store programs for later, or "save" them, the icon was born from the physical object.

Sharing, conversely, doesn't really have a real world example to base the icon on. Maybe two hands exchanging things? Perhaps two arrows to illustrate the ability for things to go both ways? Maybe a set of interconnected dots to show the connection between things? Any of them could work, so the iconography is less clear.