Here in Ohio the Amish use buttons; it is zippers they are not allowed to use.
Abraham Troyer had buttons which aren't "plain." Amish will use hooks and eyes instead.
Amish Bishop Abraham Trevor wears a shirt with buttons. Buttons are forbidden for Amish people and their shirts are usually held together with pins. Some say it's because the Amish are supposed to be very plain and buttons are considered to be too decorative.