I've seen this so many times. The introverts and smokers I can explain, but to this day I have no idea why people congregate in the kitchen even when there's nothing specific to draw them in there (food, etc.)
In nearly every other room of the house, you're meant to sit down. The kitchen is optimized for walking between appliances.
When the available seating is exhausted in the living room, it feels a bit strange to remain standing if everyone else is sitting, so you excuse yourself to the kitchen for another drink, where you find a number of other people standing and conversing. This feels less strange, so you don't see much point in going back to the living room.
Once everyone has made the inevitable trip to the kitchen to freshen up their beverage, and gets caught up in a conversation in the kitchen, the living room gradually becomes empty, and at that point, nobody wants to go sit alone in the living room and miss all the action happening in the kitchen.
There's just something enticing about watching home-cooking. It's better than any TV you've ever seen. If your subject is a better cook than you or has a much larger range of recipe comfort, watching their technique or process is really eye-opening. I love seeing what my friends do or don't do in the kitchen, always something to learn about.
It smells amazing too being near the action. Sight + smell getting stimulated all at once.
