You may wonder how all those grapes are harvested. There are two choices: by hand or by machine. The choice often comes down to what kind of wine you are making.
Most premium wines are hand harvested, giving much more control over just which grapes end up in the fermentation tank. Often a grape vine will have grapes in various states of ripeness, some berries can still be un-ripened while others may have "raisined" and be shriveled. A skilled harvester can pick the best and leave the rest behind.
Not so with a machine harvester which shakes the grapes off the vine taking whatever falls off. The winery could have staff that sorts through it all, but that is costly and time consuming.
Given all this, you can expect that you get a better quality harvest from hand-picking vs. machine. And better grapes mean better wine.