As a child I had little experience with birds, although I do recall be fascinated with a friend's budgie, but I really never gave it another thought until I met the man who is now my husband. He'd had birds, was quite involved with them, but a combination of tragedies (egg binding, beak and feather disease) and defections (person who took bird for a two-year period moved to Hawaii with it, Amazon bonded to his mother like superglue) had left him bird-less for some time. I met Sake, the Amazon (who predeceased his mother, unknown cause, only a few weeks before she succumbed to cancer) and I began studying up on birds and visiting them in pet shops and so on. We always planned to get a bird, he thought a GCC would be good starter bird, but we were biding our time waiting for the right moment. Then Scooter happened.
But that's more how than why. I love my kitties and I find them quite as worthy of affection. But a bird is a bird, not a cat. They interact differently, they learn differently. Their social behavior is different. I think it probably boils down to the combination of their being visually oriented and oriented to using vocalizations to communicate -- these things make them more "like us" than most mammals, and that makes the relationship quite different to what we have with other companion animals. MHO.