I wouldn't say it stems from my insecurities, but I do keep in mind that it would take a lot to get to know her, and if I made friends with her, it is HIGHLY unlikely that we have any interests together (science, imagination, poetry, romantic things).
Usually hot girls KNOW they can get any guy they want, so the spend their teen/20's with guys who they WISH were decent people, but aren't really, like the party animals, the street racers, the bad boys, the cool guys etc. Later in life when they realize that the spent their early years getting on with their looks, and that a younger generation will have a better chance with the guys they once liked and that the guys they liked will have little ability to maintain a relationship, the tend to go out and use what is left of their looks and personality to find a guy who has it made becasue he didn't go out partying every week and spent his time doing something useful.
Although this isn't me, I go out partying every week and still get high distinctions in science at university, but I choose not to go out with hot girls, because I have little faith in them to play 'the game' fair and stick to me, they would be happy with a solid foundation, but would rather venture out and find more exciting people, which is fine.
Long story short, I don't find them intimidating, I just hook up with them at parties and kind of forget them, but I wouldn't trust one of them with my heart nor the amount of effort I would put into a relationship with a girl.