Hybrid vigor is not a phenomenon restricted to agriculture. It is a property of wild populations as well. Numerous ecological studies are focused on the amount of genetic diversity in wild populations. Small populations with low genetic diversity suffer from inbreeding, and thus poor physical qualities, compared to large populations with high genetic diversity. So if that’s the case, why don’t we let our fields be continuously open-pollinated, like our ancestors did with landraces? The reason is that we still benefit enormously from plants that consistently fulfill specific criteria essential for efficient farming, things like particular flowering time, maturity time, photoperiod sensitivity, stress tolerance, etc. Thus there is always a balancing act, and a lot of work goes into identifying plant lines that will satisfy all criteria, whether you’re creating inbreds or hybrids.