Using an Xbox gametag for cross-platform games/Xbox Achevments

A small request, if possible.
Since the game uses a Microsoft account connection anyway, why is there a random player name for cross-platform play instead of using the Xbox GameTag (Xbox Nickname)? 

Also, since it requires a connection to a Microsoft account, it would be nice if, while playing the Steam version, achievements on the Xbox platform were unlocked (alongside Steam). Many Xbox Game Studios games have this feature.