I do think that is the kind of purpose for these demo/example sites. They represent a basic concept in a visually pleasing way and allow developers / UI / UX people to take them and integrate them into the brand they are working with. For personal projects it's probably easy enough to just grab and go without thinking about it to much.

I agree with you about CSS and markup, so making something like this a utility class/setup could help it integrate well. It is an open source github repo, fork it apply your ideas and request a pull request.