Actually, those people are really important to a celebrities career. If something positive is written about a celebrity then more people will like them and they will come across more human. The media and the people that read it can become really important in turning a celebrity into a human. If a lot of negative press is written about someone then they could get a negative response which, obviously sends the celebrity into a mental illness and so on.
Also it’s a business and it’s popular, just like other businesses. Like why bother drinking coke when you only need water to survive.

they are bored with their own lives. what are you, a D-list celebrity or something?

Well, anytime the lives of people you will never meet, never talk to or never have any kind of relationship with becomes “real” or important to you…you should find a new hobby.