Problem is that "business capital" is also the same as "social capital". Rich people have influence because they hang out with other rich people.
If you want to have startup you have to hang out with rich people so they invest in it or they buy your services. You don't want to have your company 10 hours or more away from customers.
It can argued that it does not matter as much for Google, but if you are a product owner of a "FizzBuzz maker", you need social capital with high ranking people in organization so they don't cut your budget. In the end it works the same, that you have to play golf with the right people so they trust you and don't cut your funding.
Of course, it is not enough just to hang out with right people. Don't get me wrong, because hanging out with people will validate all skills so if person doesn't deliver no one is going to hang out with such person.
There was an article on HN not long ago with a line "Talent is distributed equally. Opportunity is not.", because social capital in big cities is much more valuable than in country side. In terms of money, in terms of no one is going to talk to you, in big city you can find new friends easier.