It's based in scientific theory! Blonde hair attracts more light therefore is more attractive to the eye. Nearly white hair is unusual and creates a halo effect catching the human eye. The colour is more attractive to the human eye - not necessarily the person and their qualities. It is purely aesthetic. In addition, engrained beliefs regarding hair colour are perpetuated by the media, stereotypes, etc. We *believe* that blonde hair makes us more attractive - therefore, we are act more attractive, fun, etc. Light hair also makes you feel 'lighter' as you are, indeed, attracting more light - the connotations of light? Laid-back, fun, irresponsible, frivolous and lacking depth.