In reply to Gary Bairead.

you appear to suggest that there’s only a demand from 0.4% of all WordPress sites. That isn’t accurate. It’s difficult to gauge how many sites would use a feature like this.

It's certainly nowhere close to the majority.

From the Philosophy page:

Design for the Majority

Many end users of WordPress are non-technically minded. They don’t know what AJAX is, nor do they care about which version of PHP they are using. The average WordPress user simply wants to be able to write without problems or interruption. These are the users that we design the software for as they are ultimately the ones who are going to spend the most time using it for what it was built for.