There are many tropes related to whether a parent is good or bad. But a much more common trope, particularly in American fiction, is simply that parents always love their children. So even a bad parent, who seems to have little concern for their child, or even an outright abusive parent, will eventually break down and claim everything they were doing was for their child.
This can be particularly jarring when a parent has been absent
with no good excuse; then, on seeing their child for the first time, already an adult, they may immediately claim to love them.
Obviously to some extent this is Truth in Television
. Many parents have a strong, instinctive desire to nurture and protect their offspring. And bad parents may have good intentions.
Examples: In Hansel and Gretel
the parents leave their children out in the woods at night, where among other things there are witches. But, in the film version, their intention was supposedly to hide them from witches! And it was a noble sacrifice to boot
Gone Baby Gone