> It wasn’t always difficult to migrate between computing platforms. During the heyday of the PC, jumping from a Dell or Compaq to a Macintosh, and vice versa, was relatively easy, because users had almost unrestricted access to their own files, most of which could be counted on to work across different brands.

> That portability largely ended in the mobile era. Apple, Google and a graveyard’s worth of other companies restricted access to internal software mechanisms, adopted more unique file types and “sandboxed” apps so each one had its own isolated data.

Call it a "computer in your pocket" and lock it down harder than Fort Knox so users become less computer literate over time. That's a big part of the smartphone revolution's legacy.