Why do scientists consider vestigial structures evidence for evolution?

Vestigial structures are taken as an example of evolution because they give us an indication of structures that, due to the adaptation to the environment, disappeared.

At the end of the vertebral column, we have the coccyx as an example of this.  Its believed that it could have formed a tail and currently, is only a small bone without any specific function, even some individuals are born without it.

fossil's are like over rated rocks like low key not gonna lie i don't get why we can't just call them old rocks like for real i mean i call my grandpa and grandma that smh