From the experiences snake owners who employ racking systems, not all adult ball python need hides in a rack as the rack creates a fairly secluded environment...but then other "rack" people provide hides regardless.

If you're going to keep your ball python in a glass vivarium or even a tub, two identical hides are highly recommended. =)

Oh and not all RTBs "grow out" of wanting/using hides...every snake is different and a snake owner needs to cater to their snake's needs and likes.