Some of you people too funny. Most people don't even know how to adjust the setting on their TVs. They don't even know what the settings mean. What does brightness mean? What does contrast mean? If you put more than brightness in there, then you'l have people with their settings all screwed up and that will create a support nightmare. Then, the cost of support will go up...then support will disppear...then apple will be just like the rest of them.
Other than brightness, I have not feel the need to adjust the touchscreen. On any of time tablets (android or apple), to be honest. Just because a thing can be adjusted doesn't mean it needs to be adjusted. If you had a problem with the app that spoiled your screen, can the app rather rather than faulting apple for not giving you yet another fiddly adjustment to screw up.