It is shocking that the marriages of the holy Prophet of Islam except one case, were with the women who mostly were widow and were in the high age or some of them even were old women or some of them were annoying him. If someone is after his lust, does he really get married with the women with such situations?
The different marriages of the Prophet had various reasons like:
-Strengthening the social position of women in the cases that his wives were widow or even old. Like what happened in the marriage to a woman called Um-Salamah( the daughter of the aunt of the Prophet) that she was the wife of one of the companions of the Prophet who got killed because of one of the wars, and she had some orphan children.
-A political act for establishing the connection with different Arab tribes and a means to gather them under the flag of Islam, because the strongest relation among the Arab was the family relations and they knew their son-in-law as one of their family members and they knew binding upon themselves to defend him.
-Removing the wrong custom of that time like what happened in the marriage to a woman called Zaynab and the story in short is that Zaynab was the wife of the adopted son of the Prophet i.e. Zayd. When Zayd divorced his wife the Prophet got married to Zaynab in order to practically remove the custom of that time that a man cannot get married to the wife of his adopted son.
Another point here is that as we said before, the condition for having more than one wife is to do justice among them. The history bears witness that the Prophet was doing justice among his wife to the extent that in most days he was visiting them, even in the time of his last moments he was observing their rights, it is narrated in the history that in the last days of his lifetime that he was so weak, he was transmitting his bed every day from one room to the other(to observe the right of being with different wives) and one day he gathered all of his wives and asked permission from them to be in the room of one of them and they all gave permission.