Not surprising; although I bet half the divorces were filed on or behalf of the "straight" partner. If the only reason to get married for a gay man is to have children; once the children are grown a little or if there is no children, why would a gay or a straight person want to be married to someone they can't connect with, except as BFF??? Where's the love, physical, emotional and spiritual. It really would be like dating and being married to your sister.
You love them as family and siblings but to kiss or have erotic thoughts or activities shared would feel creepy and wrong.