Coasting Uphill

I've seen lots of people on bikes (people who I might hesitate to call cyclists) riding around and coasting up hills. This happens mostly on campus and I have a feeling that they might just be riding from dorm room to classroom, but why would anyone ever coast up a hill? That just makes forward progress even harder. If you want to go easy up a hill, a good even easy pace is better than bursts of power followed by zero effort. You can coast on the way down if you like.