Humans tend to anthropomorphize, but this is filtered through cultural beliefs and forms - you do not get a highly specific concept like 'fairies' out of a general anthropomorphization, any more than people got Dracula out of their fear of the dark pre-Bram Stoker. I've linked studies here on what children believe and anthropomorphize by default, and it tends to look like 'other people and animals continue to exist even after dying'; not 'the Unseelie and Seelie folk live in hills and if you visit them, be sure to not eat any of their food or you will be their prisoner for a century'.