Without responding subjectively to any individual situation.
I think that there was once more social pressure to stay married then there currently is, which can potentially snowball this issue as many people who have perfectly happy marriages may have gotten divorced at some point earlier in the marriage when things were more difficult had there been no social pressure to keep going.
That's why it's rising in my opinion.
Not to say that this social pressure is an entirely good thing there are some very unhealthy marriages that aren't good for either spouse or the kids that people stay in due to social pressures.