[paxys]

File transfer isn't an OS level problem. There are already a million utilities that let you get a file from computer A to computer B if they are reachable over IP. Connecting the computers in a secure way is the hard part, hence the need for all the workarounds.

[bux93]

For most people, it is part of the OS though. Windows comes with Client and Server services activated by default even on the Home edition for some reason. The functionality is dumbed down and hidden though, while onedrive - which requires registering a windows account - is shoved in the user's face.