Oh, it's about that. It's just leftover from an old base 20 counting system really. Kind of like how time is still using base 60 (though it's kinda convenient for dividing), stuff like that.
Really, English is not completely safe from that. Ask yourself why eleven to nineteen instead of, you know, ten-one, ten-two...
And is made harder for them. Because it turns out the "easy" part is not that easy to do correctly, and if not it just makes maintaining the thing miserable.