When they find dinosaur fossils, with feathers, why do they call it a lizard and not a bird?

if you were to give an iguana feathers it would not make it a bird. because a bird refers to the idea that this is a winged animal. so when thy find something with feathers and they look at the skeleton they can usually decide whether or not this dinosaur had wings or not. if it does not have wings it is a reptile