Well, I've never been turned on by anyone, as it were. My standards in terms of looks are simply WAY too high for me to ever get into a relationship with anyone based on looks. As in, I'd say a certain person is ugly or only average when the majority of the population thinks he/she is incredibly hot. Talking about celebrities btw.
Anyway I'm 18 - gonna be 19 in less than a month - and I've only ever loved 2 guys - out of which only one of whom I'm actually physically attracted to as well, and the physical attraction only came after we started to go out.
So no, I suppose it's not exactly abnormal. It's best to date people you're already friends with anyway, so you already trust each other and all. Besides, you end up liking the person's looks once you start properly liking them anyway.