It's true that they can often see needs that exist in a community, especially if they're locally based. Their role as being complementary to government is valuable and important. But it's problematic when you expect charities to take the place of...or to pick up the gaps, because many charities just don't have the capacity. They don't have the comprehensive coverage, and accessibility becomes a problem. It becomes more of a hit-and-miss thing.
That said, they certainly can often pioneer programs and develop things that can be very valuable and helpful to government as well.