There are a number of download urls that are "one-time" use. Shouldn't this at least download the output to a /tmp file?

If you're relying on the previous behaviour of curl on your one-time URL, you're already in trouble, because it's been printed to a terminal and the real contents are probably irretrievable.

No. This would open an enormous can of worms, but I'll just pick one: security.

And if you're the kind of person that needs this, the solution is a one-line alias.

This would be useful for taking meeting notes, not perfect of course, but better than I think what most people do: no notes.