One reason shown here in picture. We have a problem in this part od the country with an insect pest called the "flea beetle". It's not really a flea. Anyway, it loves to eat the delicious leaves of brassica crops... think arugula, mustard greens, all the asian greens, cabbage, broccoli, cauliflower, etc. On a conventional vegetable farm, a low-cost insecticide chemical would be sprayed, taking a few minutes, and that would be it. On an organic farm, we use no chemicals. Instead, we fight flea beetle attacks by using "floating row cover", which you see pictured. Costly to purchase, and takes a lot of time & labor to lay it over the beds.
Pictured is just one of many beds being covered now at Wishful Acres Farm.