If posting notification was the only reason people wanted to get emails, then that might be true.
BUT, if someone has email notification turned on there are two slightly more important reasons to want to see your own postings in email
A local, hard record of what you personally posted. (Plus makes it easier to find and quote previous posted material.)
Local searchability and threading of an entire conversation, PLUS OTHER conversations that may be related (that are not in discourse, think bugzilla for example), using your local email client. (In this case, searching only in discouse doesn’t cut it.)
And there are occasions when I want to use discourse web posting. So for these reasons there is no suitable workaround - I want ALL postings in email.
I think discourse should aspire to be both a full fledge mailing list replacement, as well as a full fledged web discussion list.