Typically I use it to create illustration style renders that I use within pages. I create a lot of complex isometric diagrams for my current job that are interactive. So I create them in blender, chop them up, then load them in with WebGL or just slice them into image layers that allow me to create interactive elements.
Back before mobile interfaces went flat (the skeuomorphic days) people were rendering out tons of assets for interfaces. The pendulum will eventually swing back in that direction...
I'm not him. But as a front-end too my guess can be a few:
* WebGL and 3D Models
* Creation of Assets for web
* Maybe something more abstract like prototypes, flow control, etc