It might be troublesome to block other languages, especially when languages share words and word-spellings. How do you suggest WG goes about blocking languages? Adding more code to decipher what languages messages are being written in? Do all the words need to be in the language you need to block? What if a message has one Spanish word and, as a result, you do not receive the message?
I am not against a user-activated language block that would let users accept only messages from languages that you personally select. It's not like the messages are going to help you in terms of strategy if you can't understand them. On top of that, they congest your screen and make potentially useful messages harder to read while on the move in game. Think of it as building a cyber wall, if you will.
"When Clash of Clans sends its players, they're not sending their best. They're sending people that have lots of problems, and they're bringing those problems with us. They're bringing low damage. They're bringing YOLO mentality. They're bad. And some, I assume, are good commanders."