I will tell you what causes divorce, in no particular order:
1. Lack of communication
2. Lack of listening.
3. Lack of empathy.
4. Conflicting long/short term life goals.
5. Conflicting lifestyles (i.e., he's into fitness, she's not; she's into image, he doesn't give a shit, etc.)
Everything else is just a focused example of those five things. Not enough sex stems from a lot more than just a lack of libido. She got fat stems from more than too many bon bons.
IMHO, if I were to sum up the most common cause of divorce, I'd say lack of empathy. If you have compassion for and are willing to listen to another person's story and understand things from their perspective it's pretty rare that you can't come to an equitable compromise.