WebP and AVIF images are now used on a good amount of websites. I myself save my final export images as lossless WebP, and having to re-export them as larger PNG files or worse quality JPG files to upload them is a total pain. Would be very nice to allow such formats in file uploads.

Disk space usage nowadays is not big problem with such massive storage. Web browser can view it indeed, but locally on PC or smartphone you need to install software. If that software is not convenient to use on both devices (PC and smartphone), than I versus.
On smartphone with android I never show such content on gallery, so it should work as file manager instead of gallery.