I should have qualified that by saying that there were a lack of services that suited our particular needs. We ended up concluding pretty quickly that for our purposes services like Mailchimp would have been prohibitively expensive. Also, we weren't particularly interested in running a campaign oriented service, which seem to be what Mailchimp and most of the services on your list are for. I don't remember seeing Sendgrid though. That might be what we were looking for, a simple API for sending mails that aren't tied to campaigns, but which provide the template niceness of services like Mailchimp.
MailChimp also provides a great API and they even have an extended API (http://apidocs.mailchimp.com/sts/1.0/) on top of Amazon SES that doesn't cost you anything extra (you just pay for SES).