Simply, for the ultra obsessive fangirls, like my mother. If the Harry Potter film saga ends here, then there will be no end to their moaning and complaining.
Just be thankful J.K Rowling didn't write twice as many books.
Are you serious? It is most definitely crucial. For one fact some people haven't yet read the books so they need to know what has happened(you should read them, they are amazing) Second, they are wonderful so why shouldn't they?
For all the HP fans like me... for example if they didnt make 'Deathly Hallows' then that would dissapoint many fans and people might get angry. WE NEED THE HP MOVIES! If its the case that you don't like them then you can just ignore them and not watch them =]