The failure of that model are the apps which provide only short-term functionality. e.g., I'll probably only need my offline map of Brussels or that puzzle game

The failure of that model are the apps which provide only short-term functionality. e.g., I'll probably only need my offline map of Brussels or that puzzle game for a few days. But my being through with them within 96 hours doesn't mean I'm entitled for a refund-- in fact, they probably served their purpose! Such a refund model would rob developers of that niche.