Bourkes might be the exception to the rule on Grass Keets as pets. Hand-raised Bourkes do make pretty good pets though and then tend to stay tame. I have 2 females that were supposedly hand-raised but I got that at about 6 months old (at different times), when the "tame" part was wearing off... The first one would step on my finger when I got her home... but reluctantly. Every time I got her out of the cage on my finger, she would fly right back in. After I while, I could get her about 20 feet from her cage and sit on a chair with her in the next room but she would rarely stay more than a minute before flying back to her cage. I was getting discouraged but I persisted, figuring that I should get her to go on my finger every day at least - and she learned "step up" to mean, I wanted her to step up. Finally, after a couple months of this, I just opened the cage door and went in the other room... and she flew to ME! And that was it. She became bonded to me quickly after that and now wants to come out as soon as she sees me. She will sit with me for hours if I let her and she will even look for me, all around the house, if she can't find me. The 2nd female did not bond to me as much but she will fly over and sit on my shoulder for long periods if I let her. As Grass Keets, they are behaviorally different from other parrots but, once you understand this, you can bond with them better. For example, my 2 Bourkes LOVE it when I lay on the floor (stomach down) in the living room. I guess it's like I'm one of the flock. As soon as I lay on the floor, they both come right out of their cages and start running around in front of me, crawling on my arms and shoulders. Maybe my presence makes the "ground" safe? The other thing to know about Bourkes specifically is that they are crepuscular, which means they are most active at dusk and dawn. This is great for working people but it also means, during the day time, they might seem dull as they like to just be quiet and rest on a perch (or you!). So anyway, you can se with my above example, you can get pretty far with taming and bonding with semi-tame Bourkes (in my case, former hand-feds that were not worked with for several months). The really young, fully-handled, hand-raised ones seem to be easier to tame and bond with so those should present no problem to make pets out of. I should also point out, Bourkes are great fliers - no need to clip - and mine have never gotten injured (even in my 18 X 20 foot glass sun room)!
As I said, they love for me to lay on the floor with them. I guess being Grass Keets, they love the ground. They also get their food bowls on the floor of their cages because I think they like that (I don't use any grid "mesh" thing on the bottom).
This is Twitter, my very devoted female Bourke, who will sit and watch TV with me all day, if I let her. But she flies right back to her cage no problem too. A very skillful flier - no crashes - but I never clipped her (but she was half-clipped from the breeder when I got her). She is 8 years old now.
This is my other Bourke, Rosine, out in my sun room with Lindsey, my Budgie. They interact a bit outside their cages during free-flight time but they have their own cages. I'm not sure I would cage a Budgie with a less aggressive Bourke Parakeet. I have quite a nice situation - both Bourkes and the Budgie know how to fly through my house out to my glass sun room on their own - and return to their cages by themselves - so they enjoy themselves and get lots of exercise.
This is Twitter in the "pool", with Peeper, the only Scarlet Chested Keet I had that really became tame. Unfortunately, he contracted Proventricular Dilation Disease and died young. If he infected my other birds, none have shown any sign.