Why are these hackers doing this?

Well most CRACKERS (the term hacker is very broad, cracker means someone who breaks into computer systems) just do it for the fun, others do it for money. If you are getting mad then call the police. computer hacking is a crime, people have been sent to federal prison for doing it. And if the police don't do anything (hacking isn't enforced as much when the victim isn't a company) then call your ISP provider and get your IP changed. Also try turning your computer off when your not using it (sleep mode is not the same as off)