BOYS! why wouldn't a guy date a female friend that he finds 'hot' or super attractive?

For the same reason girls don't want to date a guy friend even if they admit he's attractive. What they have as friends is too valuable to risk losing. If you and Mark ARE that close, there's every chance that during the month you were together, he found that it felt a little weird crossing that line. He admits you are attractive, because you are, but that's not the only thing that matters in a relationship - undeniably it has to be there, but if the overriding feeling is attraction, but "this feels weird", then it won't be a comfortable relationship.