I did a small amount of contracting for a local real estate company who only had their site online certain hours of the day. I asked them why, and their response was that they only had the one server, and during certain hours they needed it for processing new listings and database work. This was apparently such an intensive task on their budget server that the web server became unresponsive during these operations.
They also said their analytics showed that no one ever visited the site outside of business hours. This wasn't what I was contracted to do (and I wasn't in position to fix it), so I didn't bother to tell them that when they shut down the web server their analytics stopped running as well.