Cos they can! We all may at times either find ourselves victims of malicious rumors and gossip OR be perpetrators ourselves.
For the perpetrators all I can say is..get a life! Yes.. pronto. Clearly the life you lead must be very sad for which reason you need to constantly speak ill of others.
As for the victims well know that God created all kinds. Just be glad you are the one spoken about and not the one speaking. Pity them losers and deal with them in a manner than will bring you justice and not violence and anger that can never be any good in such situations. Ex: If you are working and find out workmates are gossiping about you, you might consider reporting them depending on the level of seriousness of their acts.
In my pre hijab days I once had to tell on this gal who was spreading vicious rumors about me and my boss which was harming not just my reputation but my career as well. I hoped she will be warned but due to the fact that she had already done other misdemeanors, she was fired. And while I was sad she lost her job I still feel she had to be set straight.