The same reason non-Slavic would be oblivious to Russian even if it were the primary international language instead of English both languages don't have that much in common. The Latin alphabet is not a problem for Russians because they practically grow up with it, while Cyrillic, if I understand correctly, is not that easy to learn if you don't know it. Still the Russian language doesn't feature articles, and that's the dealbreaker for most Russians as it is almost impossible to understand the concept without much practice. More than that, Russian grammar is not that strict and grammatical meanings are in most cases expressed differently (instead of auxiliary verbs word endings are used). Also the whole negative attitude towards West is still pre levant in our society and that's why knowing English, though preferable if you want a decent job, is not something that is expected.
Another reason is that English lessons at schools are really terrible here. Back in the Soviet Union the language that everyone learned at school was in most cases German, and when it became English, there was a distinct lack of good teachers that is still evident today.
But I believe I'm good at English and many Russians I know are. The kids you encounter in TF2 or wherever are not representative of the whole nation.