Making life choices different from the societal standard (e.g. not wanting children or not wanting a marriage). Sure, if your own desires are incompatible with that you might need to find someone else but a lot of people who do go with the societal standard actually just do so because they never thought about alternatives and have a rather romanticized notion of that default option and might still grow to regret it later which can then often lead to breakups/divorce if that only happens to one partner in the relationship. People who make different choices at least thought about what they want. Basically you want a partner who has already thought about these and not one who only discovers their actual preferences on these options a few years into your relationship.