I stopped wearing diapers when I stopped soiling my pants. Not because it wasn't cool, because peeing your pants is cool, but because I learned to not need diapers.

Same with bibs, cribs, and holding sometimes hand to learn to walk.

I can say with the highest level of confidence that learning to ride with training wheels then graduating to riding without them, in no way had a negative effect on my childhood development. In fact, it helped me learn how to ride a bike, greatly expanding on my childhood development.