Why make a movie that is so very little like the actual story?

Is the purpose really just to use a somewhat well known name? There is bastardizing a story, then there's this which has a threadbare resemblance to the original story.

Don't get me wrong, I am not saying the original story was perfect or even great. But if the writers/producers aren't going to use anything close to the original story why bother to use the name? I just wish that if the writers/producers wanted to use their own story (which is perfectly within their rights) use your own names and try for some originality.

Sig, you want a sig, here's a SIG-sauer!