For the same reason babies crawl before they walk. Hopping is easier, they have to learn to walk.
Edit: It depends on the bird. Robins hop, and so do most sparrows. Mourning Doves walk, but they are just as big as a robin. It does not depend on age, but instead species.
No, hummingbirds don't walk; they hop. I had one on my porch once.
Birds and humans..otherwise, all other animals walk on all fours or have to hop on two feet, not walk. Kangaroos and wallabies walk on all fours and hop on two, so there's a big difference there.
There is a type of frog that walks it lives in southbamerixa in brazil
Birds move in the air by flapping their wings to generate lift and propel themselves forward. On the ground, birds walk or hop using their legs and feet.
Perigrine falcons spend most of their time in the air as do most birds, so they don't "walk" they hop, and they probably don't do it very fast.
The hummingbird hovers, as with a helicopter, but a different chassis .
No. Echidnas do not hop. They walk.
they walk
When on the ground or a branch robins use their legs to walk or hop. However being birds they are also capable of flight.
Hop
No. Both hop or jump but neither can walk.
Animals which walk on just 2 legs are called bipeds, they are bipedal.