first of all, Tauri used to be almost hungarian-only, so you could say that talking only in hungarian is a habit of the past. Secondly, a lot of people can't (or even don't want to) speak a foreign language, so they just stick to hungarian.
In real life maybe yes, but that's not something I've experienced online. In EU servers a lot of players use their own language, making team communication almost impossible. French speaking french only, turks speaking turkish only, and russians using their runes, etc. It is ofter annoying, but you can't force a player to use english only, that would be discrimination. Not to mention that it's the same in Asia server as well. The ones who want to coordinate will of course speak english, but the rest will use their own moon runes in chat.
I would say that it's a matter of will. Do I want to speak a foreign language, or just use the one I'm best at? As I said, it can be annoying, but there is not much you can do besides asking them to speak english and hope they will do it.