

Hehe, I get that. However, if adopted properly, it would be a practical language skill, as it would be a language officially in use. Besides, if those studies described above are to be trusted (not sure if they are), it would facilitate additional language learning. But that argument is what you are getting at with your comment on Latin?
The idea being that eventually (though that would need to be far in the future) you would not need to translate as it is a common language among all member states.
Because it is a difficult language to master and it puts many non-native speakers at a disadvantage. As pointed out above, there are only two countries who do speak English natively now, but depending on your native language, some citizens still have an substantial easier time learning English.