[badsectoracula]

> I feel like the OSs should be shipping runtimes for it

Well, Windows does come with the MSHTML control. Sadly for some reason they decided to version lock it at IE6 instead of keeping it up to date for applications to use.

[WorldMaker]

Windows 8+ added the HTML/JS native application stack in the WinRT/UWP modern application world. That stack is a lot nicer to work within than bad old days trying to script MSHTML to do what you need, if you give it the chance.