They spend hundreds if not thousands of hours developing a virus just to crash someone's computer who they will never see or hear about. It's literally like the most pathetic thing you can possibly do.
One of the funniest myths about ``hackers" is that they're trying to crash your computer or corrupt your files.
For the most part hackers are trying to achieve a goal that requires a large host of organized computers to achieve, such as spamming advertisements. They don't want their botnet to be discovered, so their worm operates in the most unobtrusive way possible.