Back in the day, most people lived agrarian, rural lives, but now, the entire world is urbanizing. As people live in cities and suburbs with transportation to deliver "fresh produce" to supermarkets and grocery stores, people generally don't pay attention to the season or the weather when they eat. They just want an avocado whenever, wherever.
But, the big truth is, the supermarket "freshness" is not as fresh as you think it is. The food may be picked before they are even ripe, may be ripened by a ripening agent for marketability and presentation, and may have to be transported long distances to reach the exact destination. In contrast, if you grow your own food, then you would typically pick the food when the food is fully ripe and ready to eat, and then eat on the same day. If your harvest is more than you can chew, then you will probably have to preserve the produce in some way, shape or form; and that involves canning, drying/dehydrating, freezing, freeze-drying, fermenting, salting and pickling.
Preserved foods are not as bad as you think they are. If you want to eat fresh that is actually fresh and ripe, then grow your own food in your garden or apartment. Otherwise, preserved food is the better deal. You are essentially eating ripe food that is grown and preserved (canning, pickling, salting, freezing, freeze-drying, dehydrating) by other people. Plus, they are just as nutritious, some even more nutritious than the so-called "fresh" food in supermarkets.
Frozen fruits and vegetables, for example, are picked at peak ripeness and retain way more nutrients than fresh fruits and vegetables. Canned fruits and vegetables are also picked at peak ripeness and retain Vitamin C longer than fresh produce. You just have to be aware of the BPA lining of some cans and unwanted food additives. Dried beans and pickled cucumbers are also preserved foods that you can find at the grocery store. White rice can be purchased in big bags and have a long shelf life (up to 5 years in the pantry); they can provide sustenance to any meal.
If you don't have a garden and self-preserved foods, then you can just buy one of those commercially sold preserved foods. These preserved foods may be canned, dehydrated, freeze-dried, frozen, fermented, salted, and pickled. They are just as good and nutritious - sometimes even more nutritious than the commercially sold "fresh" foods.
If you can eat your entire harvest in a relatively short period of time, then great for you. You don't need to preserve your food. But if you are like most people and want to make sure that the food will last longer than a few days, that's when food preservation comes in handy.