Why do film makers modify a true story?

Answer 1

Often, the "true story" they are using as a basis for the movie is inspiring, but does not have all the necessary makings of an actual 2-hour (or so) film. It has to be modified to tell the whole story within that amount of time, and also some things from the 'true story' need to be removed or exaggerated to make a great film that people are interested in watching. Sometimes the 'true story' makes up only a small portion of the finished movie; the screenwriter or directors use their creativity to decide the rest.