I get their desire to have a single unified system that manages everything, but our situation is: we use Mandrill to send the System Info emails on https://www.whatismybrowser.com to thousands of people per month. We have absolutely zero requirements for a mailing list.
If they're asking us to pay for a whole system we won't use; it's not even a discussion, we'll be leaving and they lose money.
Go figure.
MailChimp's competitors must be rubbing their hands in glee.
Personally, I don't blame them.