Why did the Plains farmers give up on crops such as corn?

The main reason farmers on the Plains stopped trying to grow the crops they had grown before they went West was that they realized the weather was simply not suitable. Because it was so dry in the West, it was difficult to break the soil, which meant the farmers needed to acquire better ploughing equipment. Meanwhile, there was extremely limited rainfall, which led to drought and subsequent fires. This drove farmers to innovate new types of dry farming, and to import crops from other dry places. Another problem was pests; many Plains farmers found that local grasshoppers and other wildlife ruined any crop they actually managed to grow.
The Plains farmers were extremely adaptable and quickly learned that doing things the way they had previously done them would simply mean they wouldn't have enough food to feed their families. The only solution was to change crops and tactics.