Problem with smart quotes is that it is different than normal quote. So for computer it is not the same. Of course algorithms can be adjusted and things work, but the quotes aren't the only problem. There are also double quotes, nonbreaking spaces, soft hyphens, tabulators and many other things, that can be considered the same. And it is a lot of work to implement that on every place.
As for Google, it "works", because they ignore it. You can also search without ' and get the same result.