Maybe bad modernist design or the out-of-favor brutalist design. Modernist design does not favor large slabs of flat concrete. Really, no form of design does. So, it's really just bad design.
Even brutalism wasn't for big empty slabs for a plaza.
I've heard that cities are going that way to make pop up events easier. I don't think it really makes it that much easier though, and it looks like shit when an event isn't going on.