I think we did not make contact because we are still to primitive and they don't want to bother to have bigger contact with those 'aggressive and primitive natives'. They just issue to us some warnings from time to time by visiting us and leaving just after. We call that "close encounters". One lady who claimed she was kidnapped by aliens said she asked them who they are and where they came from and they showed her map of universe asking her does she know where her planet is ? She said no and they replied then there is no need to explain you where are we from". :)