When you're at a lower floor and you're trying to go down, but its a time period where traffic is trying to leave you can end up in a situation where nearly every elevator going down is already full. So you call for down, cab arrives but is already full, it goes, you call again, another comes, its already full, rinse/repeat. Sometimes there's not much up traffic during that time, so it can be a legit strategy to just go ahead and call on the up and ride it all the way instead of waiting and hoping for space coming down.

Although I guess that's not quite what you're talking about.