I have been receiving this email since yesterday. Just like any email phishing, the content looks legit from Blizzard until you hover over the link and it shows you a different URL redirect:

The link it asked you to confirm your details looks like the legit Blizzard URL (us.battle.net)
The actual link is different (us.battle.net.login.yz-login.com)

Im sure there are people who can easily notice a phishing mail when they see one, but there's still many people who don't.

Why is internet banking scam via phishing still common? Same reason.