A few things you might not have known about email
Sometimes email is considered a Web 1.0 technology, when in fact it predates the web. SMTP is part of the most basic plumbing on the net and has several advantages over newer, faster, “real-time” interactions.
As we explore our solar system, the biggest determent to communication speed won’t be the bandwidth, but the latency. As bandwidth gets larger and larger, we’ll quickly become aware of the real bottleneck in the network. There is an upper bound limit to the response time, the speed of light, which cannot be broken. There are ways to get around this, but they are hacks at best and can certainly be improved.