Researchers on our planet pay way more attention to some forms of life than others and it could be the same with these hypothetical interstellar species - maybe convergent evolution has led to countless similar situations and nobody's rushing out to do their thesis on yet another planet full of bipeds who like hitting each over the head and burning each other's dwellings down.
Even the most common and mundane organisms are still subject to much study. If primitive and violent sapients are indeed common throughout the universe, then there will certainly be those wondering
why that is. There will be those looking for patterns, similarities and differences among all the different primitives that somehow manage to still keep cropping up.
Even something as common and "boring" as
sand has more than one person studying it on this planet alone. And interstellar alien civilisations will, by definition, be orders of magnitude larger in population than our piddly one-planet civilisation. A single Dyson swarm around one star could contain enough alien astronomers for each of them to be assigned their own star in the galaxy to study.
I think popular science fiction has done society kind of a disservice, by failing to impress upon people just how
titanic even just an interplanetary civilisation could get, never mind interstellar or galactic civilisations. Quantity becomes a quality all of its own.
The hedghogs, squirrels and birds who frequent my garden must see my house and garage or my car but have no conception that they are artificial or play a role in human civilisation.
Those animals might not realise that houses and cars are artificial constructs, but they certainly know enough to fear humans as potentially harmful agents. This is where I think the analogy breaks down, because as far as we can tell, there are no agents out there to fear. Just a great wilderness that might be intimidating in its vastness, but certainly doesn't display any malice.