Even if two species existed that had similar soil, water and sun requirements, had similar properties regarding taste, processability, etc., it would still be easier to farm just one instead of breeding both for milennia and splitting the means of production.
Even if two species existed that had similar soil, water and sun requirements, had similar properties regarding taste, processability, etc., it would still be easier to farm just one instead of breeding both for milennia and splitting the means of production.
Until a disease pops up, that targets your only crop. Example A: bananas.