Think of a child car seat.
If you are a parent you probably had one (or more) in the back of your car as your children grew up.
Under most circumstances your baby started in a baby carrier and then progressed to getting strapped into their child seat (often with a lot of squirming and shouting).
Eventually your child is comfortable, securely seated and safe.
Eventually they get too big for the child seat, moving on to a booster seat, and finally they sit in the car just like everyone else.
Imagine, that for some strange reason, the child has to use the same little seat forever!