Question about apps when upgrading

I just received my new iphone 4 32gig today. I previously had an iphone 3gs 32gig and backed it up right before activating my new iphone 4. Once activated I selected to restore my iphone from my previously saved backup and everything moved over except my apps. So my contacts, voicemail, recent calls, email settings, etc is all perfectly restored. I was wondering why none of my apps have transfered as it would suck to reinstall them from itunes and lose all of my saved info inside every app. Thanks.