If Samus was given some kind of love interest, there would be many bricks shat across the world, I'm sure. Despite what some people may already think, THAT would be what ruins Samus' character, not the explanation of her feelings and her past.
I'm sure people don't think about why she's seems so driven to protect everyone. If I lost my whole family to space pirates, I wouldn't want to lose anyone else I cared about.
Also Ben, don't you even start.