The big problem with sterility is taste and nutrition. It turns out that many of those vitamins and flavor compounds that we like are natural fungicides, pesticides, and preservatives. That's part of the reason why a home-grown tomato tastes so good--it's spent its whole life fighting off attackers while the bland industrial tomatoes have been protected by farm chemicals. A sterile greenhouse or vertical farm would create produce that was bland and less nutritious. You might be able to trick your plants into fighting by introducing controlled stressors (like a weakened pathogen, maybe?) into the "farm."