the visitors must have loved their human skins..
because they were ALWAYS wearing them!! Diana and Charles were married with their human skin on..Lydia and Diana had them on during their combat..Diana had her human skin on during her ritual bath..they put make up and glitter on them..teased their fake human hair..soldiers on the ship wore human skin UNDER their uniforms..ect..
Everyone knew what the visitors looked like so they didn't need to hide themselves anymore..esp in the privacy of their own ship!!
Yes, I know..the actors had to be seen..but if it were real they would be proud of their lizard forms!