Imagine I want to copy an image from a webpage into an email... And then the paste fails because the email client tries to download the image but doesn't have the correct cookies and fails...
Or I want to copy a file from Google drive onto a USB. But when you copy from the Google drive webUI it just copies the name of the file, not the file itself...
Or I copy an image from Google images and the thumbnail low Res version is copied rather than the full res version.
Copy and paste, and drag and drop, seem to be neglected on the web.