Birds don’t need ladders. Some birds climb ladders, though that’s mainly when we put them in cages. You wouldn’t put a bird in a cage and then give it a birdhouse, would you? No, you wouldn’t, because that would be silly. The answer to Terry’s question, however, is probably the answer to Edna’s problem from yesterday, which is “Because people think it looks cute.” People do a lot of illogical and impractical things just because we think it will look cute.