Why do wives seem to stop wanting sex after being in a marriage for a long time.?

In my case, it was because I took her for granted and over the years grew a strong sense of entitlement to get my way all the time and stopped thinking about what I could do to make her life better. -- I realized I was not being the husband I wanted to be but I did not think my wife deserved any special treatment, now that I took her for granted -- I finally realized that there is, and never will be any other woman in the world that has given her time and self to me to the extent my wife had -- and therefore there is no other woman in the world that deserves to be treated special by me other than her --- So I started acting like the best husband I could with NO STRINGS attached and with no expectations of getting anything from her in exchange including her appreciation -- I did this for both for my sake and hers -- Now our 24 year long marriage is the best it has been in over 20 years -- When I stopped being selfish and self-centered everyting got so much better -- as cleche as it sounds it turns out that I have been very blessed by giving to my wife that I was trying to get from my wife. -- By me taking a position of serving my wife full time, I became the husband I was intended to be and my wife is now the wife I always wanted. -- Hope this helps. It is probably from working full time and being a wife and mother and house wife she is out of time. Their are not enough hours in the day for a womans work maybe if you could offer to help her in some ways such as cook once in a while or clean on the weekend for her it would help I promise. Belive it or not if you just did something such as flowers when its not birthday or anniversary or a certificate to get a manicure and pedicure she would melt. Coming from being a woman who has alot on her plate, and my husband does do these things it makes a difference. hope you dont think I am being hard on you just trying to help good luck!!! you used the same move to many times. think up a new one, tell her, and make sure she likes it!