Ethylene is a natural hormone in plants, which promotes fruit ripening. This gas is continuously produced by fruits and vegetables and unless surrounding conditions are in control, it can lead to excessive ripening (rotting) before packaging or during transport making them inedible.
Fresh produce is also constantly under the attack of pathogens in the air like mould, fungi, bacteria, etc.
While controlling the temperature, light, humidity and carbon dioxide-oxygen ratio (such as in Controlled Atmosphere (CA) storage), can reduce the speed of ripening and prevent decay, direct removal of the ethylene and pathogens makes it much easier to extend the shelf-life of produce especially for produce with high sensitivity to ethylene or diseases.
Above, we see that a large number of common produce is prone to attack by air-borne pathogens and ethylene sensitivity. We have all seen mould on lemons and strawberries - this is due to spores of mould in the air. We also see that placing apples and bananas close to each other can accelerate their ripening - this is due to both fruits producing and being sensitive to ethylene. Of course we can separate these in our homes. But spatial segregation during large-scale transportation and storage can waste a lot of space.