It is important to make sure that any proof or evidence is not lost, altered, or destroyed. For example, if you are in an automobile accident, repair work should not begin until detailed pictures have been taken, preferably by a professional. Additionally, you want to allow for data from the vehicle to be extracted before it is lost or damaged in a vehicle repair.
Similarly, if you are bit by a dog, you want to preserve any torn clothing. If you have a slip or trip and fall, your shoes may be critical evidence. You do not want to wear, repair, or throw out your shoes until the case is resolved.