Why do commercials get cut-off early? No seriously, why?

You have got to be high to put that much thought and effort into this question (not that there is anything wrong with that). If advertisers get their money I would think they're pretty much over the fact that it's getting cut off. And I don't think every company has a person watching every channel in every state at all times to keep track. Commercials don't get cut off by accident, they get cut off because programmers are obligated to run the commercials, and I don't think they specify whether or not they run the whole ad, only that it's played so many times in a certain time period. As many sponsors as possible in whatever time allowed.