Every writer wants their readers to care not only about their characters as individuals, but about the connections between those individuals. We want to hear that they ship two characters, or that the fight between those two friends broke their heart. We want them to obsess over the slightest touch of two characters' hands.

Characters don't necessarily need to share the same interests to be compatible. A romantic partner doesn't need to be described as the most attractive person in all of existence. It's something else entirely that makes character relationships believable, relatable, and shippable.