Web publishers should definitely be stripping metadata at least, and transcoding isn't much harder. For anyone who cares about bandwidth, transcoding to efficient formats is non-negotiable; if you don't, then why do anything? Just ship PNG, who cares?

I think one of the compelling use cases for camera manufacturers would be an interoperable format for editors. Since JXL has support for so many channels, you could load your image into an editor, edit it, add layers, etc., and export as JXL, which could be used for other things.