Salam
As for 'marry again to control desires', I find that downright pathetic. One who cannot control his desire after marrying one lady, will not have his desires met by another. He will surely fall upon another lady who is likable & subsequently desirable.
The whole point of being a muslim is to please Allah (SHW) & do what he has commanded & allowed us to do but go no further. If one cannot control his desires after being married, then he clearly does not understand Islam.
And Alhumdulillah we have Prophet Muhammad (pbuh) as an example.
WaALiekum Assalam
That's the way I feel about that as well. I'm glad you mentioned it. In Islam we are told to lower our gaze. And I believe there is a hadith where Aisha says that Prophet Mohammad (pbuh) was the best at controling his desires. And he is our example to follow. I think that reason would also be very offensive to the wife especially if she was doing her best to help her husband as well.
Edit: Yahya related to me from Malik that he had heard that 'A'isha, the wife of the Prophet, may Allah bless him and grant him peace, would say, when she mentioned that the Messenger of Allah used to kiss while fasting, "And who among you is more able to control himself than the Messenger of Allah, may Allah bless him and grant him peace?"
Bukhari 1826
Correct me if I am wrong but I don't believe the Prophet (pbuh) married just because, he married widows and people that needed care and to strengthen ties between the ummah. I don't mean any offense by this. And I know it is halal but I think we shouldn't just say "it's the right of the man to have more than one wife." You'd gain more reward InshaAllah by marrying a woman that truely needed a husband and not a never wedded woman hardly out of her teens.