Excellent place for code reuse.
I have two objects, both of which are almost identical, except for that one of them has to use a unique id, where the other one doesn't. Inherit, override, and reuse most of the code.
I just saved myself some time recoding the exact same thing twice.
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche