As a partner at YC for over 10 batches now, I've worked with lots of great founders who have come from all over the country, and many make having families work. The cofounders of MongoHQ both moved to Mountain View with their families (with kids) during YC, and it was a crowded house but a productive one too. It can be done.
There's also nothing that says you absolutely have to stay in the Bay Area afterwards. Many founders head back to where they come from if that's the right thing for the business.
what does the bay area offer that requires someone to uproot and come out there just for a few months?
what if the location they are already in is ideal for their business? for instance i live where we have 3 cent per kwh power, moving to SF to work on anything power intensive will increase my startup costs 5 fold at a minimum, and that is power alone, let alone everything else being 5x more costly. the insistence that people come to you is strange to me.
There's also nothing that says you absolutely have to stay in the Bay Area afterwards. Many founders head back to where they come from if that's the right thing for the business.