Where is this hypothetical user going to find a keyboard, mouse and airplay display (and maybe a dock)? If all those things already exist, then having a CPU ins

Where is this hypothetical user going to find a keyboard, mouse and airplay display (and maybe a dock)? If all those things already exist, then having a CPU inside one of them is a lot easier than trying to make your phone act like a desktop. In the end, if you have cloud/continuity/whattnot, what problem does this solve?