Hi @psweb I disagree with your point, and I believe this to be an important feature that should be included, in my 20 years as a developer, I always have include files that do database calls, either if I am working with Drupal, Wordpress, or my own custom CMS made in php or python, I also have Webassist tools, and I was able to add any SSI file full of database calls without a single issue.
Again a simple example with a side bar, many of the systems I had to build have a post or news list of recent news this has always been on a side bar for example or at the footer with a repeater of the 5 last or featured, if my system has user accounts, I tend to show their name always on the menu or side bar, with a small thumbnail of their picture, some of my systems the user on his profile page selects either to show his email or social media urls and icons, I do that storing a relation table in the database and with case or conditions the system knows if it should show it or not, on a big site, not having dynamic data on Include files is a terrible idea, since if you need to do a change to the side bar you can end up editing a ton of files instead of just one.
I also hope this gets implemented it is kind of the basic of a good site to have dynamic data on include files, that is kind of the hole point of having include files.
My personal opinion i do not see it useful for only static html.