Even in cases where you are not uploading to a site to sell photos/art a lot of websites where you submit any sort of image needs to have it in their T+Cs that they can do a shitload of things with the image just so they have permission to share it to other people, move it between servers, process the image (compress it to save space) etc...

those all were ok until generative AI came on the scene and now those same terms is like giving cart blanche to the site if they want to create or fine tune a model.