Copy image from one place to another. Copy entire powerpoint slide between presentation. Copy table from web to word.
for the latter programs having the default be paste with formatting seems fine. yes, i'll paste stuff from the web without formatting. But copying/cutting/pasting within the same document is also a pretty common interaction and if i'm cutting something non-trivial (eg. google docs table/nested lists), i don't want to paste it back into google docs as a bunch of regular, separate lines.