Said it plenty of times before, but one thing I really liked about Martha was she wasn't running away from a mundane life or some other personal issue to go with the Doctor.
The more I think about it the more I find this reasoning for liking her to be really weird. If she was so happy at her job and her home, why did she go? Obviously she did find her life mundane.
And why should it be a bad thing for people to join the doctor because of that anyways? The Doctor himself is running away from something, it's kind of a central theme of the show.