Although most endulge in the idea of aliens conceptually abductions don't occur in the physical realm, it's more of an induction into an ethereal realm, one in which information flows together like cosmic stew. The higher forces don't manifest a form but there has to be an interface to work with… channeling 1000 different languages into a communicable wavelength takes some work, hence why they manifest in the simplest form understood to us.. recognizably human but oh so alien