Why did I buy Emerald? Not because of Mew, but because I have only my sister as a friend, and yet, she doesn't play pokemon often, and in order to make sure that pokemon are ready for the real battles, I wanted a pokemon game that not only makes making a competitve pokemon easier than the other games combined, but also contains a place that tests out your competitive battling ability, and that's why I bought Emerald: It has the Battle Frontier as the place that tests out your competitive battling ability, and more...
But, yeah, I agree that it's "sly". After all, we don't want another pokemon that might become just like another Celebi in terms of availability, only different(Celebi doesn't require a Wonderspot item that many are probably not going to get, given the time remaining until the next-gen Revolution console comes around, while Mew, the pokemon that might become another Celebi in availability terms, does)...