I'll elaborate even more on Steve's post. Think of it like this. The kit makers make their kits fairly generic. I will use French Merlot for an example. In a kit, a Merlot is basically a Merlot, but if you go to the wine shop you will find numerous Merlot's. Let concentrate on just the French Merlot for an examplethough.
You will see many different French Merlot's that all have their own distinct characteristics that draws you to purchase one brand over another. Maybe it is a different type of oak or the soil types of their vineyard, pruning techniques,or any other feature that makes theirs different than their neighboring vineyard.If they were all the same, the cheapest one would be the only one to survive in the market. By each label putting their individual twist on the winemaking process, some are better than others.
By tweaking a wine kit we can experiment to make a wine to our personal tastes plus it adds to the romance of making your own wine. If we always made kits to the letter of the law it would be no different than buying a box cake mix of the same brandand making it the same every time. Sure, there are other brands of cake mix that taste different just as there are other brands of wine kits that will taste different.
Most all that tweak their kits realize they can trash the kit with a mistake but fully realize it before they attempt and are quite aware of this and take full responsibility if it comes out a flop. I have tweaked a couple kits that were not to my expectations but it was still fun and a learning process.
Since the majority of us do not have our own grapes to make our own wine we just start with a concentrate kit and begin our own personal winemaking journey from there. I want my Wine Expert Merlot kit to taste different than your Wine Expert Merlot kit. I want my own personal wine that gives me a sense of accomplishment. There are limits I can do but hey, it's fun.
Now those that are new to the winemaking process, I have to state that you should follow the directions to the letter of the law with your first few kits to get a feel for everything and also stress that if you deviate from the directions, you do at your own risk and void the fine warranties that most kits offer. Ask lots of questions
BEFORE you experiment and if you have an idea, throw it out here to see if others have tried what you want to do and see if they had a success or failure.
This is my disclaimer for those that always follow directions and hold them as Gospel.
Smurfe