Exclusively breastfeeding is very challenging to do while working, for one. Even at my megacorp with a dedicated space, a hospital grade pump, and 2 hrs a day dedicated only to that, it was a substantial hit to supply. Considering that most women don't have those amenities and support I'm not surprised they don't breastfeed exclusively after their mat leave (for most women in the US, 6 weeks unpaid)
Not to mention - it can be painful (if I had no option of course I would endure pain for my child, but there is no shame in looking for something less painful) or the baby can not learn to latch (formerly known as "failure to thrive" and a driver of infant mortality)
I've recently become a father and I do wonder how much US maternity leave (or rather, lack thereof) accounts for your high formula usage.
While my wife is coping, it's still very draining to handle a newborn and pump at regular intervals, even at 10 weeks. If she was in the US and had been forced to go back to work already, she may well have given up on breast milk already.
Not to mention - it can be painful (if I had no option of course I would endure pain for my child, but there is no shame in looking for something less painful) or the baby can not learn to latch (formerly known as "failure to thrive" and a driver of infant mortality)