Even if they use the outhouses, they may still be going back to picking in the field without having washed their hands.
True. In Mexico, they do use toilet paper in their houses, but then put it in trash cans, because their sewer systems apparently cannot handle the TP. It’s similar to India, where the tradition is to “wash” with the left hand, eat with the right, because their sewer systems cannot handle TP.
NOTE: That’s not true for all Mexican sanitary systems. At the hotel where I stayed in La Paz, Baja California Sur, in 1991, the system took TP just fine.