Well for one, RSS is pull. This is push. RSS also requires that you subscribe. This wouldn't necessarily require that.
Needing to subscribe is arguably a feature. In fact, if subscription was required on the protocol level like RSS spam would be impossible (for some values of "impossible").
So... when is it that I pull an email sent to me from the SMTP server of the person sending it? Pulling it from the server to the client to read it doesn't count as email being 'pull.'
The difference is that with RSS you are pulling from the source not pulling from your personal 'cache' (unless you use a web reader like Google Reader, but even then Google is pulling from the source; RSS updates aren't being pushed to Google). The email equivalent would be querying all SMTP servers out there (or a subset) to see if they have mail for you rather than hitting up your IMAP/POP server to see if anyone has sent something to you.