Let me stop you right there. Nobody ever feels like it. Ever. Not once. Got that? No? Okay, I’ll continue.
This is an oft-used tactic; so much so that you may not even notice it any more. What it boils down to is this: someone is asking you to do something while relieving themselves of the guilt of doing so. When it’s someone you know, say a friend, it’s very close to “I hate to ask you this, but…” When it’s someone like your boss saying it, the general idea is usually this: “I know this is not part of your job, in fact, it’s part of mine, but you have to do it and I’m only phrasing it this way because it’s not really your responsibility. If you don’t do it, believe me you will hear about it.”
I know, that’s a lot of subtext, which is why this method is used so often, and why it works so often. So put yourself on the other side of it; if you find yourself doing this, or about to do this, stop and try to think of a way that might be more polite and, more importantly, more honest to the person you are about to ask a favor of. They’ll appreciate it, even if they never know it.