YC is a for profit company, they're looking for a return on investment with the occasional "non profit" to impress the community and feel good. If they don't feel you have a big enough idea or can generate a big enough return you get rejected. Sometimes you can but other startups got interviewed first. There's only so much space. You shouldn't be that defeated. There's a lot of us that applied over the years and didn't get chosen. Never take it personally. Sometimes there just isn't room.

I love NewsLines.org by the way.