Ergos hip belt takes the strain of your back and shoulders, and the ergonomical position the baby naturally sits in is much better for the baby (knees higher than the bum, instead of hanging by the crutch)
Facing forwards can also leave the baby unable to turn away from all the impressions when they get tired. Facing your parent gives the baby a safe place to look, they can rest their head on your chest and they have a perfectly good view sideways if they want to look at something else but their carrier.
