interesting question, no?
possible reasons:
(1) the more beautiful the woman, the more they realize they can have any number of men, why settle for one for very long? i.e., s*x-lib has changed everything.
(2) modern men have not kept up w women's needs, and they get bored quickly? i.e., women have changed, and men have not adapted in a way acceptable to women? If so, why have men not changed, and further, is it realistic that they can? Is it feasible that they do so? Or would men lose more than they would gain by making the supposed needed changes?
(3) men refuse, or are unable, to see the red lights she is flashing months in advance, leaving her to be the one to finally say "bye"? male ego might be the key in this possibility. But this begs the question: implicit in the fact women do the breaking up, is the idea that it is the women who dislike committment, not men (every divorce I have ever seen it is not the man who wants to break up, it is the woman, have seen this five times just in the last two years, most cases also before that). Is this in turn a function of modern societal conditioning whereby the woman has accepted the modern premise that women should not want men? With the resultant
outcome that women have a subconscious discomfort with any relationship from the start (or at least soon after it begins) that serves to utlimately bring the
relationship to an end, albeit, in a way neither the man or woman truly understand? move on to the next one, repeat "self-destruct" process.
(4) "singleness" (% people who are single) has risen dramatically in the last few decades. In turn, there are far more people of both genders available for flings,
thus increasing the temptation to wander, putting pressure on relationships that once would have been a lifetime "done deal". The s*x-lib culture=single culture,
creating a far more difficult atmosphere for monogamy than was the case , say, 45 yrs.

There are other possiblities of course, these are just a few. I suspect it is a combination of these things in many instances, who knows? Please know I am not saying women are "wrong" to leave a relationship, of course a woman should have that right. Am only asking "why" this appears to be the case so that men can gain better understanding of women.

Because the men are usually too cowardly to so just that.
How many men have had the courage to say "hello", not to mention "goodbye"?

Lilly-livered, emotional cowards!

.

By 2020 we will have more female millionaires than their male counterparts.
Ambition and success gives confidence in self and where the I is strong, the We must realise that there are 2 strong people in the WE and only true values of respect, companionship, support for eachother and some tolerance for partner's weaknesses , not financial control, physical pounding as women make more money all ghaddifi methods to control them is becoming powerless.
Its a chan
ge that will adjust itself in future to give room for mutual respect as that is the only way forward

It is the by-product of western civilization. The #1 reason that women divorce their husband is primarily because of money.  75% of broken marriages in the West are initiated by women, in some cases, the man did nothing wrong to warrant such behavior from the woman.

In the west (North America) there is a huge financial benefit for a woman to break up her marriage for whatever reason that she can come up with, expecially if the man is rich or suddenly wins a million $ lottery.  At least she will get 50% of the man's wealth and everything that he has got.

A woman living in the West might consider breaking her marriage for one or more of the following:

1.  The man is rich and have the resource to pay her divorce settlement running into millions of dollars after the breakup
2.  The man wins a lotery running into million of $ and she want 50% of the money
3.  She  has a new boyfriend and want to move in with him
4.  The man is jobless and can not take care of her
5.  She is sick and have bipolar disorder
6.  The man is a  cheat, a drunk or abusive
7.  The man is too loving and caring and threat her like a queen  ( see the youtube video part 1 and 2 below)

Part 1

https://www.youtube.com/watch?v=U93BBNq5A64

Part 2

https://www.youtube.com/watch?v=MONNcL1Rglw&feature=related