If you have read up about Multics, or perhaps used the AS400 in the past, you might be aware of the nine primary goals which the Multics creators first outlined in a paper that they published back in 1965. One of those goals was to have the operating system be continuously operational in the same way as a public utility (such as water or electricity) operates. This was an interesting idea, and it is one that we have since witnessed in the AS400 and to some extent in the UNIX and Linux operating systems. However, it is something of a departure from how many people actually use their computers, so it might be worth explaining why continuous operation is such a desirable circumstance to operate under.
A continuous operating system allows a computer to be available to you 24 hours a day, 7 days a week. While you might not be using your PC all of the time (after all, even programmers and systems administrators have to eat and sleep occasionally), it is definitely reassuring to know that if a stroke of brilliant inspiration does happen to strike you at some point in the wee hours of the morning, you will be able to log in and begin the process of bringing it to life. After all, some of the greatest advances in the history of the world came about because of the inspiration that only a nap can provide.
You also need to consider that once you get away from one lifestyle and one time zone, there is a serious need for a system to be able to operate all of the time. Imagine that you are in South America, one of your colleagues is in Europe, and still another is in Australia. You can all get on at a time which is convenient for you. But for the others, it may be best to log on at local convenience.