Hand-me-downs are not necessarily imposed by the parents. There are kids who see their big brother or sister wear something and they want to wear it too
Grew up classic middle-class, and my mom would ask me what I wanted from my older brother. Whatever I didn't want would get donated.
I can see Kayla being overwhelmed by having to take all the kids shopping, and using hand-me-downs as a simple way for the kids to have clothes. Also I can imagine that it is something that you just do in more conservative, religious families as something that appears as what people did "in the good ol' days"