Now, in addition to the point /u/ameya2693 made, understand this:
Rape is a sexual assault usually involving sexual intercourse or other forms of sexual penetration perpetrated against a person without that person's consent, right?
It all depends on consent, yes?
Nevertheless, when you marry a person, you sort of give him/her the right to assume that he/she has your consent, now I am not saying there cannot be sexual intercourse without consent in a marriage, but I am saying it's not as black-and-white as others try to make it.
When you live together with a person under one roof, there may be a thousand different interpretations of the same situation. And who will interpret a signal in what manner, is very difficult - if not impossible - to tell beforehand.
That opens up possibilities for very complicated misunderstandings, including those about the expression of consent, and in such relationship, definition of rape may and is bound to become absolutely vague and opaque and much depends on the veracity or accuracy of the accusations and counter-accusations.
Also it's not like the man is getting anything he didn't already have before with the wife's consent, presumably several times, so what's the fuss about?
But the new thing might be physical struggle the wife could put up, and that takes it in the domain of domestic abuse.
I am just saying, in a complicated situation, a person, especially the one who passionately 'thinks' she is being victimized, may tend to have very simplistic and naive definitions of the words like "consent" and "rape".
During such times, it's not unusual for two honest people to have very different understanding of the expression of consent and what is rape.
He might think that he has only mildly coerced his wife into having sex with him that night, and it's not even rare, while she may later realize - often upon instigation of relatives - that she was raped. That's just one example, possibilities are limitless. I draw the line on physical violence, not the intercourse, and that's why I put emphasis on "domestic abuse".
Prosecuting someone on the sole charge of "marital rape" is simply not feasible.