I can get the transfers between friends part, but why between platforms? That makes zero sense from a business standpoint.
The only way that would work is to have game companies manufacture and distribute an external storage medium themselves, because platforms sure as hell won't say "Oh you bought a license on another store? Sure, you can use our CDN for free!". And now we've almost reinvented game CDs.
Don't forget about moving their possessions. I don't know if houses in America come fully furnished, but there's no way you could sell all your furniture for enough to buy it all back in a new state.
Also people surely have things that they would not want to sell, for personal or practical reasons, right? To pretend the only thing people need to move is themselves feels a little heartless.
And we've not even talked about people with families yet...