It is very common to see attraction for opposite sex in world because this attraction is very common and opposite sexes always attract each other. The one of main reasons of this attraction is sexual attraction. We start feeling this attraction from earlier age and this attraction continues for whole life. Generally, this attraction remains same throughout our life with some variation in intensity of attraction. Attraction for opposite sex is very natural phenomenal; therefore, there is nothing wrong in it.
It is even proved in various studies that a small child can feel this attraction. As we grow in this world, we learn to control these feelings and not show others what we are feeling because sometimes, other person of opposite sex may not take our feelings in good way. Mostly, these attractions lead us towards emotions like love. People start finding person of other sex so much attractive that they look for possibilities to go near that particular person. Many times, these kinds of strong attractions are known as love because person feels very strong attraction for person of other sex.
There are many great love stories present in our world where we can find great examples of strong attractions between people of opposite sex. These attractions motivate us to meet this person again and again; therefore, we look for possibilities to always remain close to him. Every human being moves through numbers of such attractions throughout his life and therefore, we get attracted sometimes towards totally unknown people of opposite sex.