[JohnFen]

I don't think it's related to data not being "with you" anymore. You'd find that even if you did keep the data "with you", you'll still need the layer you're talking about.

The reason for that layer is performance and that a uniform way of working with data is desirable. Particularly if that data will be accessed by more than one program or instance of a program, regardless of where the data actually resides.