In some countries, it would make circumvention easier, in others, harder. For example, while most websites were blocked in Cuba, you could still use Delta Chat over IMAP to communicate via the national email provider.
In my opinion, it adds to a well-rounded ecosystem if a given messenger supports as many ways to deploy and as many workarounds as possible.
In the specific case you ask, you could already tunnel TCP (IMAP & SMTP) inside TLS/HTTPS/DNS with some hacks and boxes at the right places. This would be a topic for another conversation, though.