Why customers dont write reviews?
These customers are angry about their experience. They had an expectation, and it wasn't met. Their review is a form of catharsis; they're looking for a way to vent to relieve or reduce the emotions they're feeling.
Why does my Facebook page not show rating?
A Page's rating is based on multiple sources, such as the reviews and Recommendations people share about business Pages on Facebook. Only Pages that allow Recommendations may show a rating, and a Page may not have a rating if it hasn't received enough Recommendations.