My theory on this is that because they have developed this games which was a big hit back in early years and gained a lot of players and respect a long the way since then, it makes sense, tho the COD is the worst FPS I would say, the repetitive gameplay and most of the time simply copy & past and that's why every year we have useless COD game. There are many F2P FPS's which could compete with COD but because COD is so popular it's still gets a lot of players all around the world even tho this game doesn't deserve it.