I take a photo with my phone. I want to post it for plant identification or some other worthy SO purpose.
I try pasting the Google Photo sharing URL into the Image box. Rejected with 'unsupported format'. I try downloading it and then uploading it. Rejected with too large. I try uploading it to imgur for myself, downsizing it in imgur, and supplying that link. Rejected due to 'unsupported format.' ORLY?
When downloaded, the file is a jpg. The last problem here is noted in another question: imgur likes to offer useless html page links instead of actual image links. Seems to me the uploader could learn to deal with those. Similarly, Google Photo provides a sharing link which is not the image itself, but to facilitate this use case the uploader could recognize it and do what's needful. At very least, a checkbox to permit downconversion of uploaded file would save work.
Why not accept Google Photo and similar links and downconvert, or offer to downconvert?