Sales people and last minute IT requests

Ok, what is it about sales people (and employees in general) that they always wait to the last minute to request things from IT? It's afternoon at say 5:00PM. Why is it that these people wait until now to come to the IT guy with lengthy new requests that just have to be done right then! I'm here all day working on other issues and could have made time during the day to do whatever it is (i.e., SOW review, security document, write something for a customer). But now, it's 5PM and it's always, "We've got to get this to the prospect right now!!!". Ok, so why do I have to rush to get this done when they can't plan better? I'm just at a loss at this behavior.

Of course, if you don't do whatever it is, then management doesn't consider you to be a team player. If you do it, then that bad behavior is reinforced and these people assume it's ok to do it again. This is a no-win situation. I just can't figure out why people can't plan ahead better and give a day or more or ask the prospect for more time.

An emergency on someone else's part does not make it an emergency on mine.