Because gossip at best is criticism that the person does not want to give to the other person's face, and at worst is a form of character assassination.
Reasons why people gossip:
2. To influence situations.
3. To convince others that they are right about a situation.
4. To strengthen alliances (which comes from reason 1).
So these are my rules about getting free of gossip.
1. Only deal in facts as they happen.
2. Ignore what is said about people.
3. Recognise that there is no such thing as criticism - only feedback.
4. Do not question another's focus/motives (i.e. he/she only did it because.....)
5. Be confident.
6. Be honest about your limitations.
7. Don't try to predict the future.
If you work in a gossipy area, there's no need to make any big gestures. Simply change your attitude as above, and lead by example. If people are smart, they'll follow you. The rest.... well..... give them enough rope, and they'll hang themselves.