Ah, so young and naive.
You are quite right, when you hire someone you should be looking only at the qualifications and aptitude of the person for the job. Unfortunately you also have to look at the whole person.
How are they dressed, how do they speak, what is the overall picture of the person? How will that person fit into my office? A cute e-mail addy isn't a deal breaker, but it says volumes about the person and personality of the applicant and when I hire someone one of my top criteria is being professional. Unless you're a hooker, cocktail server, or child actor, cute isn't professional.