I generally just don’t enjoy gaming on a tiny (comparatively) phone screen as much, but the extra screen real estate lets me take in a lot more information at once, which was really vital, esp. early on when I was learning what cards did (and even near the end, since you continuously unlock new stuff for the first couple dozen hours, there were new cards that it was easier to read/study on PC).
Plus for multiplayer, having it up on a second monitor so I could do stuff while my opponents made decisions was a boon.