It is not just the hybrid vigor. In fact, I would say the main advantage of the F1 hybrids is actually lower phenotypic variance of the crop.
Sure you will have hybrid vigor in an F1, but you can get that vigor with a four-way cross of pure inbred lines too. But the four-way progeny will also be highly variable.
If I were a farmer I too would want the consistent low variance of F1 isogenic progeny. An inbred line optimized for environment X could work. In some (rare) cases engineered inbreds can be even better than F1s but they may not work well out in the real world of environmental flux.
Sure you will have hybrid vigor in an F1, but you can get that vigor with a four-way cross of pure inbred lines too. But the four-way progeny will also be highly variable.
If I were a farmer I too would want the consistent low variance of F1 isogenic progeny. An inbred line optimized for environment X could work. In some (rare) cases engineered inbreds can be even better than F1s but they may not work well out in the real world of environmental flux.