One of the main reasons to jailbreak your iPhone, is because of the apps which are not available on the regular iOS will be made available to you after you jailbreak your phone. So stop asking yourself Why Jailbreak iPhone 4. Go ahead and download the right app to jailbreak your phone and use the restriction free version now. It is more helpful and you can even do things like download themes which may not be available on your existing iOS. You can make all the changes you want on your iPhone 4 be it major ones or minor ones.