If someone gives you a videogame controller and asks you to play the game, your first question would likely be "How do I play?" This is a simple way of asking "How do I control what I see on the screen?" A game's controls are a major part of the gameplay as your player's input essentially determines everything. An otherwise good game can be rendered unplayable by an awkward or overly complicated control scheme. This is compounded by the push toward touch controls that, especially in the mobile game market, demand a simple interface with a lot of developers opting for a one-touch gameplay.
Just because game controls are trending toward simplistic, it doesn't mean you need to shoehorn your game to work in this fashion. The most important thing about your control setup is that it needs to fit to your game's style. You won't see one-touch controls on a first-person shooter just like you won't see a memory game that requires two joysticks and eight buttons; it just doesn't make sense...