Why move to San Francisco? One of the benefits of living in this day and age is that you can start a business from pretty much anywhere in the world. Sure, it is presumably easier to acquire VC, talent and deal with general logistics if you're located in the valley but still... It's pretty obvious that leaving your job, friends, moving to a different city and living off your savings is a high risk move vs staying where you are and working from there. Not knocking you or anything (I don't know your entire story), I'm just saying.
If I were to start a company now, I'd probably stay right where I am and keep my job until I saw a level of success with my new project.
I think he answered the question- he was looking for funding. You can do a great many things remotely these days, but investors want face to face meetings, so you have to go to tech hubs to get them.
The connections, venture capital money, talent, and general startup/technology environment aside, San Francisco is an amazing city. By the far the best place I have lived. I don't regret moving one bit.
If I were to start a company now, I'd probably stay right where I am and keep my job until I saw a level of success with my new project.