If that's the case, let it be a feature of image editing packages that can output formats that are for the web. It's a web standard we're talking about here, not a general-purpose image format, so asking browsers to carry that big code load seems unreasonable when existing formats do most of what we need and want for the web.

People generally expect browsers to display general-purpose image formats. It's why they support formats like classical JPEG, instead of just GIF and PNG.

Turns out people really like being able to just drag-and-drop an image from their camera into a website - being forced to re-encode first it isn't exactly popular.