My guess why Intel added hardware JPEG decoding is HD webcams. Most of those do MJPEG, so with a hardware JPEG decoder and a hardware h.264 encoder videoconferencing can almost completely avoid the CPU. Most external higher-res webcams also only do YUV (for low fps / resolution, as it quickly exceeds USB 2.0 bandwidth) or MJPEG, some newer ones do h.264 though. Incidentally, all those cheap HDMI USB capture sticks (I think most have the MS2109 in them) also use MJPEG.