In reply to Blair Jersyer.

Templating-related features have largely taken a backseat in WordPress for years. Even the addition of get_template_part(), one of the biggest features over the last several years, was just a wrapper function for existing functionality. Not much has changed, and theme authors have been left to their own devices.

Often, tickets like this just need someone to champion them. Many of the people with the resources to make improvements to the templating system just stick to building things in-house. They see 8-year-old tickets like this and don't think it's worth their time trying to get in core. So, until someone comes along to really push something and get approval, it just sits there untouched.