Yes, a chest strap on the backpack is very important. It ensures better weight distribution and stability of the backpack on the back. The chest strap prevents the backpack from slipping back and forth or feeling uncomfortable on the shoulders when walking. In addition, the chest strap can help to reduce the strain on the back and thus prevent pain on longer hikes or when carrying heavy loads. All in all, a chest strap contributes significantly to the wearing comfort and health of the back and should therefore be retrofitted if not available.