I'd say the purpose is more or less to show respect. By phrasing it as an idea or a suggestion, you give them the chance to (appear to) cooperate willingly. Bo

I'd say the purpose is more or less to show respect. By phrasing it as an idea or a suggestion, you give them the chance to (appear to) cooperate willingly. Both people presumably do know what's really happening, and this is exactly why it's seen as unnecessary (and inconsiderate) to actually say it. There's no reason to call extra attention to something unpleasant.