First of all not all men objectify women but generally speaking men objectify women to some degree. The primary reason men objectify women is because of the position we are in, in the dating world. Men are expected to make the first move. This means that we are the ones getting denied and take the brunt of the emotional tool when a women says no.
When a young man starts off in the dating world he inevitiblty feels the first few stings of being denied. This is when he realizes he needs some sort of internal defense mechanism to stop the emotional hurt of being denied which usually takes on the form of objectifying women. This decreases the amount of hurt the man feels because the women he pursues no longer mean as much to him.
In theory we should handle this situation by expressing our emotions in an appropriate manner and eventually getting over it but men are not taught that. We are taught to never show emotion. This is why we quickly choose to just objectify women so that we can pick up and move on quickly from one women to the next until we find our true love.
I think that society is becoming more and more accepting of men who express their emotions. However, there is still a visible stigma coming from some men and women against men expressing their emotions.
Men reading this, please realize that expressing emotion is not a sign of weakness but really a sign of strength in facing the truth of the situation and eventually overcoming that truth and moving on.
Women reading this, please realize that men treating dating like a game is caused by our need to not show how hurt we truly are. You can help the situation by never making fun of a man for expressing emotion when he is hurt. Also, by making sure you always let a man down softly when you don't want to go out with him. We are in a difficult and competitiive situation so we don't need to be hit while we are down because we really do feel emotions just as badly as you do, we are just trained to never show it.