When your daughter needs to write an essay does she do it on a phone? Probably not. The usability of mouse and keyboard are important for games, because it affects the types of games you can have. Notice how a lot of phone games essentially play themselves. You only have to press "go do the next thing". That's very different from having to navigate the game environment itself.

Voice and camera aren't really usable input mechanisms for most people. Camera will kill your battery life and voice recognition won't understand most people (English is not their first language).