... Birds are very prolific in urban and suburban areas. And even if someone reaches their teen years without ever seeing one out in nature, they'd almost certainly see one on a screen, or in a book, or at a zoo or pet store.
I know birds are very prolific, but I'm talking about baby birds. For all the sparrows and crows and gulls and pigeons and whatnot around, how many people do you think have seen their babies?
The only baby bird-deficient place I've ever lived in was a suburb that was so newly built that it took some years for birds to settle and build nests. (though a good variety of species were present flying around)