There're network effects between teams in a big company just like there're network effects between startups in a big city.
As others have mentioned, the big tech companies are all actively doing this. Nevertheless, it's not really taking. I know 3 people who moved from Google's NYC office (the 2nd largest) to Mountain View because all the top-priority projects were in Mountain View. As a general rule of thumb, you want to be where the executives are, and the executives are going to be at headquarters because a.) that's where their home is and b.) that's where all their most productive people are.
There's a steady conveyor belt where young single folks move from satellite offices to headquarters when they want to advance their career and then older folks move to satellite offices when they have kids, to be with their families or enjoy a better quality of life. This is healthy in the sense of maximizing happiness for everyone, but it means that the most ambitious, highest priority projects and most talented people are going to cluster at headquarters.
(As a side note, I feel like not enough people understand that the cost-of-living in SF is an effect of the wealth that's been brought into the area by the tech industry, and isn't just a random fluctuation. If some other metro area suddenly had a large concentration of successful companies that paid high wages, the cost of living would go up there too, until COL-adjusted salaries equalized peoples' preferences for living there.)