It's more than just the picking, digging and cutting. There are processes such as sorting, rejecting, grading, packing, etc. It's not unskilled work because there are time limits, quotas. They're not just out there wandering around with a basket, picking the odd apple between fags. It's intensive work. And skilled in many aspects. Not medical professional skilled, but experienced nonetheless.
Anyway, would you want yobbo Bob and his mates handling your cucumber?