I know, right... as opposed to when a 5-7yr old moves into a booster and we can brag about them being mature enough to sit properly the whole ride, learning to buckle their own booster correctly every time (with us worrying parents checking their work, of course), and then also crying that our babies are that old and not babies anymore.
Heck, same goes for when our kids go ff... we can celebrate that their heads are more proportionate to their bodies, that their skeletons are more fused than they were before, and that their heads don't flop as easily when they fall asleep so they are comfy even though they aren't being cradled in a reclined position. Heck, that's what I focused on when I had to turn Ruthie at 2.5yrs old