One answer is very simple.  We already know how to effectively and efficiently grow corn and soybeans.  Jatropha curcas is a relatively unknown crop for this area.  There is limited knowledge as to establishment, pest control, seeding rate, fertility requirements or even what soils are most optimum for production of said crop.  That knowledge would take at least 5-10 years of fairly intense research to develop.  In that time frame, both corn and soybean researchers would have improved their crops and introduce adaptations to overcome many of the limits you mentioned.