It has little to do with cellular memory and more with what aminal we as people have developed from. Birds are not the only flying animals. Bats and insects can also fly. To be able to lift oneself in the air, the muscle mass and the weight must be distributed in the body in a different way than those in a human body. There are several bids like astringes that cannot fly because their muscle mass over time was redistributed.

As for the human desire to fly, if only our head wasn't that heavy. )))