Mom used a treadle machine for years. I don’t recall much about my childhood, but I do remember when she was pregnant with one of my younger brothers, and she was piecing a quilt. She couldn’t treadle because of her “condition”, so I sat across from her, treadling, while she did the sewing.
And I understand that treadle machines still are the ones that sell the most, as sewers third-world countries use them for industry. (Don’t know if that’s true or not.)
I've done mission trips to 3rd world countries. They do use the treadle machines. Not sure if for industry though. The ones I saw were being used for teaching young women to sew.