Story

No one cares about file size anymore. Even mobile views of your typical news site page are multiple megabytes in size, between useless embedded video/animated gifs, dozens of tracker .js files, slideshows, using html/css to resize full resolution images, etc.

5-10 years ago when bandwidth was a premium and substance mattered more than style, maybe WebP would have caught on. Today, general users don't care, they just want the shiny things.