Why does that seem strange? People who are interested will know or course, but to 99.99% of people, “dinosaur” specifically means lizards (often huge) that lived millions of years ago. Even the name means “terrible lizard” and a lot of people might remember that. They’re conceptually so far from birds that the relationship is naturally relegated to a tangential factoid.
Conceptually they are very different than sparrows or robins, but if you get up close to a Cassowary one has the distinct impression of meeting a modern Utahraptor.
They're actually utahraptors hiding inside bird skins. They snuck out of the armageddon in costumes and they just wander around trying to act natural now.
I mean, we don't think of ourselves as lobe-finned fish either.
That's because we aren't lobe-finned fish... But birds are a type of dinosaur
Birds aren't just a "type" of dinosaurs, they're literally defined as the surviving dinosaurs and their closest extinct relatives. For all intents and purposes, what we call "birds" are simply dinosaurs.