Assuming women divorce because they have better options than their husbands, how is it that divorce is so common?

According to Rollo man's SMV goes through the roof right when marriages start to fail (mid to late 30s) while women hit the wall and should theoretically cease to have good options.

Boredom? Lost Frame? Irrationality? Unused potential of men? What do you think is the main cause of divorce from the male perspective?

Edit:: Let me condense the top answers in this thread:

1) Many men do not in fact max out their SMV.

2) Women are not rational when it comes to SMV estimation. They overestimate their own value and underestimate the risks of ending up alone.

3) Divorce laws further minimize the risks of divorce for women.