When people will start thinking that Blizzard is not a charity but a business with goals to earn as much cash as they can (just like all other businesses out there). If you find peace with that idea, you will find yourself less disturbed by things like pet store.
It's like complaining that automobile companies release new models of cars every year. Or that mobile companies make new phones every year. Isn't that milking too? I am also unhappy that I have to force myself (oh that word again) change my mobile phone every year because new one has better features than previous one.
So Blizzard also creates something new to get more cash. Just deal with it and be happy that they created World of Warcraft at all.