Farmers produced rice and wheat because govt encouraged them like that. In 1960s there was huge food shortage in india especially north india - even rich people in delhi used to be nervous. So they started this mandi system in punjab/haryana which is near to delhi and encouraged and forced them to keep on producing rice and wheat guaranteeing them MSP and setting up mandi's to collect the crop. Now there is enough food means you dont destroy the system and throw the farmers under the bus.