The taxi driver who takes you to your hotel from the airport is probably making something at home that we would classify as art, but they don't have any word for art because they don't make a fuss about it. The concept of art and the artist is not a human universal. The desire to make stuff is a human universal, but placing the stuff and its makers into a special category called art is characteristic of extremely complex cultures like ours. I say this because I don't want you to think that I'm arguing for this quiet time in the design process as some kind of a mystical thing, or because I want to put game design creativity on a pedestal. All creative people share this, from Picasso to some guy building furniture in his garage.
Game development is a business with schedules to meet and money to make.
The vast majority of the time, our actions are dictated by purely pragmatic considerations. But it is still a creative process requiring imagination and inspiration, and those rarely occur in meetings. There's a period near the beginning of the development process when the thing a designer needs most is solitude. Ernest Adams is an American freelance game designer currently living in England. In a much earlier life he was a software engineer.