Because PNG is not suited to this kind of use. PNG is primarily designed as a replacement for GIF. Different image formats are useful for different things. And JPEG XR will greatly extend the capabilities of JPEG, far beyond that PNG can manage - and PNG can't even measure up to today's JPEG for photos.
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Because PNG is not suited to this kind of use. PNG is primarily designed as a replacement for GIF. Different image formats are useful for different things. And JPEG XR will greatly extend the capabilities of JPEG, far beyond that PNG can manage - and PNG can't even measure up to today's JPEG for photos.