I've seen this in all industries, not just startups in the Bay area. Above a certain level in companies proples personal lives and work life's are intertwined and inseparable. These people tie their self image, self worth, and entire life to work. Once your like that, you have no way to interact with the world and other people other than through the eyes of business. Every meal, mixer, person you meet is a potential new business asset to leverage in the future. Their entire world view is different.