Maybe this is the same as "To remember the already checked emails and not re-download them the next time", but it's not uncommon for me to wash a batch of mail from my laptop and have a few that I want to download right away and others that I want to download to another pc. If the default was something like "Release" and I had the option to mark selected messages as "Hold" I could get and act on the ones I want to and download the others later without having to download them immediately and then forward them to myself for later downloading on the pc. Maybe the POP3 limitations mentioned in the other suggestion would prevent this, but it sure would be handy.
