Why would anyone believe in love at first sight?
Sure, it's an appealing thought, but when you REALLY think about it, it makes no sense whatsoever. Lust at first sight makes sense, but not love. A crush can happen instantaneously, as it is merely an infatuation based on immediately observable traits (usually physical appearance), but there is no way a person can truly LOVE a total stranger from the very first moment their eyes meet. I believe the only exception to this is a parent's instant and unconditional love for a newborn baby.
Imagine seeing a stranger on a busy street, and you find yourself suddenly head-over-heels in love with them. And then, just as suddenly, that person steps out into the street, is hit by a car, and dies instantly. Aside from the obvious trauma of watching a person die violently right in front of you, you're not going to be heartbroken for life over the death of that total stranger, are you?
Now I do happen to believe in the possibility of forming an instant bond with someone you just met that very day. While it wouldn't be a strong bond like that you share with close friends and family, you can already tell that there is something special about this new person, and that the two of you will become fast friends, possibly more than friends. But it is not true, endless, unconditional love that you feel for them just yet. That takes a liiiiittle more than a single glance at a stranger to achieve.