App Demos

Wow i really think apple needs to put in features so app companies can give say 5 day trials or demos of there app. I know there are lite versions of apps but for example i would definetly want to demo the garageband for ipad before i got it or the djay for iphone before i got that and there not gonna make lite versions of those. So i really think apple should put in features to allow developers to give demos or trials of there apps. also i think it would slow down the use of installous. anyone agree?