Actually, it is not always true that an app needs access to WiFi and pictures to be used. Often it is just to collect data about you, e.g. position, place, habits etc.
It is slightly different as example, but I remember that they made an experiment in London: they installed a free wi fi in a very turistic place (like Trafalgar square). To use it, you just had to accept the conditions. Easy, isn't it? Well, among the contract's details, they asked you to swap your children ! The experiment shows that none of us read the T&Cs and that accepting them criminals can use this connections to steal data and information about personal details, such as passwords or message contents. We should be very careful about what we download on our smartphones!