The article claims that Schema has not caught on, but in fact you have to be approved [1] to be able to have Gmail pick them up in emails you send and it's not really an open standard like it should be.
Moz has a great article which covers it pretty well. Basically you have to send 100 emails per day for some length of time.
Since you can't just add them to your email and expect them to work, I think that is why it hasn't caught on. I'd really love if it did though.
1: https://developers.google.com/gmail/markup/registering-with-...