Stirrups attaches to hip belt and gives little feet a place to rest and improves the comfort for both you and your baby. They facilitate a better sitting position for your baby and releases pressure off the baby's sacrum. Baby's weight is better balanced and distributed between your hips and shoulders so you can comfortably carry for a longer period of time.
The stirrups prevent older babies from accidentally kicking you while you are walking or throwing you balance off by swinging their feet.