Somewhere it said that in some primitive cultures the woman just squats on some leaves to give birth. I think it makes sense that childbirth would be less painful if the woman is vertical - gravity would help things a bit. In modern day hospitals the woman is quite horizontal. Perhaps squatting would also help in addition to the gravity.
Have you or someone close to you given birth in a hospital lately? My wife has had two kids in the last few years, and was offered a wide variety of options for birth and labor positions. The squatting position was even recommended to her more than once. One reason it’s so often done lying flat in bed is because of epidurals. Once you knock out all sensation below the waist, it’s not a good idea to try standing, squatting, or moving around.
Many people do squat, but the labor and delivery process is not really limited by force. The muscles of the uterus are more than capable of moving the baby out - the long delivery and pain is necessary because first you have dilate the cervix and then move the baby through the vagina. Gravity will not help you stretch faster without tearing.