Maybe but I wouldn't be so sure. Mobile browsers today don't use JPEG hardware decoders and for a single frame HEVC isn't _that_ expensive to decode. I believe the argument is that hardware decoders are inconsistent (what you can decode successfully depends on what platform you're running on) and have high latency due to needing to pass the data back and forth to another chip in the system. For something like HEIF which also lets you store short videos as a replacement for animated GIFs you'd still want hardware decoding at least some of the time though.