Difficult to offer a one size fits all answer here. People will either contribute or not to a particular cause for a whole host of reasons - personal and family experience or circumstances, their own attitude to charitable contributions, the extent of their existing charitable giving commitments, whether or not they are in a bad mood when they see the appeal - all sorts of reasons.
For myself, although we now live in a global village with a range of social media and news outlets, I think many people are suffering from charity fatigue. All the adverts now are designed to be hard hitting and to pull on the heart and purse strings - to trade on peoples decency and guilt - and their is a limit to what people are inclined to support. I regularly donate to causes I deem of value - cancer research, World Wildlife Federation, marie curie foundation and the NCB - and I feel disinclined to give to any more.
In fact, I get quite irritated, irrationally and unfairly in all probability, at being approached in the street by people waving a collection bucket, or the continual adverts placed in some leading papers for (I think ) the cleft palate society.