Taking risks is building a COMPANY while having obligations such as a family, and mortgage.
I could be building the next most profitable company in the world for all you know. The bay area isn't the be all end all for internet based companies. It's foolish to require that they be there. That's like requiring your staff to be in-house when you run a software company.
I will tell you this right now, my obligations mean I can't leave my small town in Iowa. I don't care if you write a check for $10M on the spot for me to move to the bay area. My family is worth more than anybody can ever offer me.
To your point: >> The reality is that there are tons of other people who are as qualified as this person
I think this is where industry veteran may have an edge compared to "other qualified people" as you put it. Yes 20 years old founders are great for many reasons, but experienced veteran that know the system inside-out may have competitive advantages and know-how that younger ones don't have. And if that's right, I think it would be silly for YC to not invest in them because they can't move for 3 months. Actually, some people just travel a lot during those three months (I.e. going to dinner and stuff), but still run their company in their city. Keep in mind that not all companies in YC are two guys in a garage.. some of them have 50+ employees, you can't just leave for 3 months.