A kitchen can be optional, sort of. What I think of when I say kitchen is a stove, and some sort of fuel source, a cook pot, maybe a bowl or a mug and an eating utensil. Of course this is for hot meals. While some hikers will choose to go for the cold meals, which would not require the above mentioned, which would drop weight from the pack, I don’t mind the little extra weight and have the option to enjoy a nice hot meal at the end of the day, or a cup of joe in the morning.
However, there are other things that some kitchen accessories are good for. You can boil your water with the stove and cook pot so that you have clean drinking water. For those cold nights it is nice to boil some water, put in a Nalgene and throw in the bottom of your sleeping bag for some instant heat through the night, and then you have water that is not frozen in the mornings. Also, for that frozen water, a stove and cook pot will be a quick way to melt the ice. No ice, you can also melt down snow (but to do this there needs to be some ice or water in the bottom of the pot before you start adding the snow, otherwise it will actually burn. Also, melting snow uses more fuel than melting ice.) Also, you will already be carrying something for a fire starter (as part of the 10 Essentials), so some of the fuel sources such as the Esbit tablets will work as one of the essentials.
There are quite a few options to consider when deciding on your kitchen, if you decide to carry one. What kind of stove (white gas, canister, wood, Esbit, alcohol, etc…)? What size cook pot? What kind of cook pot (aluminum or Ti, etc…)? How about a kettle? Spork or spoon? Long or short handle? Will you carry bowls? Mugs? What kind of food will you be using the cook pot for? Will you be Freezer Bag Cooking? Then there are accessories to go with the kitchen such as heat reflectors and windscreens.
So, there are many choices to consider, and many different combination’s that you can come up with. It all depends on what you need. And again, some do not carry kitchens, I like them though. I have 3 different set-ups, it just depends on what I need to do on my trip to figure out which one I will carry.