This is the only reason aliens visit Earth. Lingerie. Their species never developed fancy underwear, they had no need for it, since they have no curves. They started flocking to earth when they detected the first TV broadcasts from earth and the variety of undergarments at display totally blew their minds. They negotiated an agreement with the US government to provide technology in return for yearly samples of the latest fashions(the US was represented on the negotiations by Gordon Moore). They hide from earthlings because they are embarrassed of their scrawny bodies.