The thing is
This happens all the time with adults too. Only in the case of adults we blame the lack of willpower of the victim or recognize in them a responsibility for their own mistake of allowing abuse to continue.
We treat children different in this because we think (rightly) that they don't have the choice even if they have the will to abandon abuse (she had to put them in jail, FFS! An abused adult only moves out and it'd be over!); and (rightly too) that they ultimately did not choose the relationship that creates the abuse - parental, step-parental, school, whatever. Now, I do not think this is an ideal or natural state - it is clear to me that when children have the flexibility in freedom of association that adults have, abuse will plummet - or at least, repeated abuse will. And yet, the attachment will never end. It is so prevalent that I sincerely think it is human nature.