Whenever I see this picture I think of this:
| Creature | Swims | Walks | Flies |
| -------- | ----- | ----- | ----- |
| Dog | X | X | |
| Fish | X | | |
| Bird | | X | X |
| Duck | X | X | X |
Notice how for each combination of swimming, walking and flying, there is a living creature that can do just that, with the exception of swimming and flying.
Sure there are flying fish, but they glide rather than fly. Did evolution really forget to cover this niche?
IANAScientist, but maybe being a creature that can potentially fly onto land but not be able to walk once there was an evolutionary disadvantage, and was bred out.
You’re right, but apparently this is a trade-off that paid off for some of the creatures in this thread.