You've asked an impossible question. It all depends on your relationship prior to marriage and children as well. There's many variables (such as affairs, relationship comfort, money worries, someone not pulling their weight around the home, lack of leadership, mental instability, something really BAD you did years ago) the list just goes on and on. And why are you asking women in particular? Your issue may be that she has lost attraction to you. The environment you are creating when you aren't getting sex definitely isn't helping. You need to take action and stop talking to her about it.
My advice, for what it's worth, is something that won't hurt you and will only make you a better person even if it doesn't work:
1) Google Athol Kay
2) Read his first 2 books - The Primer and The Mindful Attraction Plan
3) Join his forum and do a triage - they will help guide you from there.
Ultimately - like everyone says.....you can only control yourself blah blah blah.....so if you make some positive changes (like get fit and lose some weight if you've gotten fat and lazy) and maybe things will get more positive elsewhere.
Also, if you're trying too hard - i.e.: "I'm doing all these noice things for my wife and still getting no sex" then think about reading Robert Glover's "No More Mr Nice Guy"
You can download all this stuff on your phone if you need to. Just don't tell your wife what your doing - this is really important. And stop carrying on to her about sex. Trust me...it doesn't help
P.S> Don't listen to namby pamby. You're a man. Continue to do man things. Women like men. Yes oxytocin provides relationship comfort - however you need the dopamine for her to be attracted to you and want to have sex with you. That's the drug you want, not oxytocin