Forgive me for waxing poetic, but: Love is deep. Love is powerful. Love is a series of personal choices made over a lifetime...or at least, as long as your acquaintance with the person in question lasts.
People simply don't enter into that kind of...perspective and level of caring for another human being based on their looks alone. And if you do, honestly, what does that say about your priorities and the way you value other people?? A pretty face is all it takes to win your soul? What about those people who you don't happen to be attracted to; are you capable of loving them as well?
That isn't to say that being extremely attracted to someone on your first meeting can't lead to deeper feelings of love later on (which tbh is what I think most people mean by 'love at first sight'). After all, you're more likely to actually TRY to help and speak to and learn about someone you want to be near all the time. But the motivation and the ensuing results are not one and the same.