Sorry for the rant, but this is usually wrong. The amount of people that just keeps their computer on is noticeable. And when I ask it's usually "just to avoid having to wait" or "I've always done that".
I personally always hibernate my computer. When I turn it off it takes more time, but I'm already on the other side of the building so I don't care. When I turn it on it takes basically the same amount of time, and it is exactly as I left it. People keep the computer on just because convenience...and I don't think it's a good thing.