There was a bill on congress's table about 10years ago saying "we need to tell people what they're eating so they can avoid unhealthful foods. That bill got watered down and the end result was "it's ok to list what's good about a food on its labels." Now we have breakfast cereals made of ~60% sugar by volume with a label that reads 'good source of fiber'. So we're doing ourselves a favor?
They could read "good source of synthetic fiber that will give you gas and cut up your digestive tract" - but honesty and benefits are sadly NOT the concern.
3g of fiber is the amount added if you want to put "good source of fiber" on a grocery store item. note, an apple has 5grams of natural fiber. counting fiber is like counting O2 molecule in the air around you. If you just breathe you'll be 'ok' - likewise if you eat whole foods as we're intended you'll get plenty of fiber. In case you need more, you can always tear off pieces of notebook paper and have a snack.
Link to the NPR story: worth a listen