For starters, cross-play isn’t common-place in the gaming industry. While this is certainly disappointing to many players, it’s not totally surprising for a couple of reasons.
Further, the game hosts separate servers for each platform, meaning you’ll only ever run into players that are on the same system as you are. Unfortunately, The Elder Scrolls Online does not support cross platform play between PC, Xbox One, and PlayStation 4. Does The Elder Scrolls Online Support Cross Platform Play?