Why do volunteers change my relatives original indexing - they have made a total mess of my tree

The FSFT (FamilySearch Family Tree) is built in a fully open-edit format. We are all volunteers working on the same tree. The good thing is that we can all contribute to it. The bad thing is we can all contribute to it. Not everyone is careful or knowledgeable. But, every problem has a solution. Every change is logged and can be reversed or corrected.