Apple takes this decission because their Youtube application license just expired .
Apple doesn’t plan to continue the existing license because of the tension that exists between it and Google. Youtube application was first present on Apple’s iPhone back in 2007. There is some tension between Apple and Google as they compete against each other in the mobile phone market. Apple also recently dropped Google Maps and replaced it with it’s own application. iPhone’s map application is developed by TomTom in conjunction with Apple.
Although the Youtube application will disapear from iOS6 after it was present on iPhone’s for 5 years straight, fans have nothing to worry about. The Youtube application will still be available for download. This is why Google doesn’t see Apple’s decision as being too harsh. Google will have the chance to monetize the application by running ads.