The effect conveys geometries and dimensions when activated that would otherwise require an animation. For simple objects this could save bandwidth and be resolution independent.

While I do not advise using it everywhere, it is just one use case that I do not have a problem with and that could be a useful part of a designer's toolset. Think of it as a 3D version of animated SVG. I only noted this because most other uses of WebGL are unnecessarily flashy and irritating.