No Alien Visits Ever

A very good reason why we're never visited by any aliens :

Distances between stars are way too great, as to preclude any
possibility of practical travel between them. Like everything, Aliens
would be limited to the accepted and proven speed limit of
c = 3E8 m/sec, and practically and likely something FAR slower.
Distance = Speed x Time. Do the simple math.

Probably just as well. If Man is any example, then aliens who would
likely be more advanced, and would view Mankind as a primitive entity
to be used at will. We might make delicious hors d'oeuvres !