As Winemaker81 suggests, you determine how sweet a wine will taste. And that applies just as much to a kit as to a winemaker who crushes and presses their own fruit. Of course, a kit may have been designed to finish very sweet, but if you know what you are doing you can do all kinds of things to control that, from increasing the amount of liquid in the must to pitching a different yeast, and from allowing the wine to ferment brut dry to back sweetening with less sugar. A wine is sweet or dry because the wine maker made it that way, either deliberately because they knew what they wanted and knew how to get there or they had little idea what they were doing and they got to where they got by accident.
