Why are they called wisdom teeth, since many people have trouble with their "wisdom" teeth.
Because they tend to emerge in our late teens or early twenties, several years after the rest of our teeth. The "wisdom" adjective, also found in languages other than English, comes from this age - by then, we're supposed to have grown out of our childhood immaturity.
My dentist told me years ago the main reason folks have trouble with them: in many parts of the world, people are reaching their adulthood with all 28 teeth present, and, even then, have trouble fitting them in, let alone another four teeth at about the time their jaws have stopped growing. Also, because the wisdom teeth take so long to develop, they can often grow pointing in the wrong direction, causing problems for them and the teeth next to them.