5. She Was Grounded
Rose had a family. She had a structure to get back to. She had a job, she had a boyfriend, she had a Mom. All these family members had a history. That's not a given. Look at Amy, who only had Rory, and barely had him at first. The Doctor said in the first season "900 years and I've never been slapped by someone's mother." That's a pretty impressive streak, and he didn't get anywhere near keeping it up for another 900 years. Rose had a grounding, and it kept her real, kept her human. Her mother wasn't wrong to be afraid of what would happen when that ground fell away. And it made all kinds of sense that she would live out her life in another universe with her family, her friend and her parents.