But we do! We see them all the time, flying above our heads and making nests where they can.
And if they’re not flying, they’re chasing you and you should be running for your life (unless it’s a kiwi), and it might have a raptor claw. Meet the cassowary.
(If you mean the big guys though, like triceratops and t-rex, it was an asteroid the size of mt. everest. The crater can be found on chicxulub peninsula in Mexico.)