Edit: I'd also add "on the web" continues to be an excuse for slow, unresponsive software. Even in ~96 or so, I remember folks getting excited. "Look at this online frog dissection thing!" ... It was crappier than what you could do with even a small download. But it was on the web so it was hot. Same thing now.
I know the full extent of the capabilities - one is just a corporate website with no interactivity. It's just dumb. The previous version was just simple static HTML; but as part of the "responsive design overhaul" it turned into this behemoth that makes several dozen requests to open the homepage. Nuts.
The Foundation install instructions first ask for three dependencies: Ruby, node.js, and git. Subsequently, through gem and npm, dozens of other dependencies were installed. The framework pushes multiple .js dependencies onto the served pages, and heavily encourages using either Compass or libsass to generate the final CSS, making it weigh considerably more. It even had tooling to automatically rebuild as a background process.
All of this, and I basically just modified the example templates slightly to help me build a layout. In theory all sorts of other things could be done with that framework, but the nature of the software stack we have, at least in this domain, favors including the kitchen sink when you need a cup of water.