Every kid who is dd's age is already in a backless booster. She's noticed it, but she thinks they look very uncomfortable and 'Not safe as houses.' (her words. :ROTFLMAO: )
I'm noticing that attitudes and expections really come more from adults than the kids. I've heard "Bored" more times said by adults that their kids will be for whatever activity, than if the kid is left alone to own devices. It's kind of a programming for what the kid SHOULD be, than what they truly are.
So, as far as I'm concerned, it's the same thing with the whole "Big kid" seat baloney. The kids don't know any better. It's attitudes that are started, then reinforced by the adults around them.
When her friend gets in my car, she happily uses the Tiffany Parkway. Her mom has tried to foist her backless booster on me, but no, I won't have it in my car. She's 4 years old and the Parkway fits her nicely. (VERY TALL child -- around 47" - no kidding, really). She talks sometimes about the backless to dd, but dd is that self assured that her BIG KID SEAT is HERS! She couldn't use the Regent before she grew, so for her, it's big kid enough.
Besides, that time driving home, when she was in the rental just after I picked it up, and the Parkway slightly tipped to one side because of how it sat -- that was enough for her to want her solid 5pt racing harness back.