"Can be relied on to _only_ deliver text" is a valuable and important piece of functionality, and a capability that has been cut out of too many protocols with no replacement in sight.
Is delivery really the problem, though? You can deliver all the code you want to an e-mail account which I check using pine and none of it will ever run. I think that the problem is that the mail clients in question have the ability to interpret the code. HTML? It's text-only, but contains a number of features that, when implemeted, produce what I think we'd all call undesirable results.
I could send a message that says:
helo somenastydomain.com mail from [EMAIL PROTECTED] rcpt [EMAIL PROTECTED] data here's some viagra I'd like to sell you --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]
