Perhaps it's just because most pirates are lazy. Downloading is the easiest and quickest way to play the game. And this is not something you could solve with today technology. Even if you could offer instant play when charging 60 euro, the 60 euro is too expensive to cover the download time of 4GB data.

I do think that in the future, big browser games can't be pirated at all, you have to pay but you can play instantly. It's just a matter of time before game piracy is gone .