The title says it all. Sometimes merchants install the app and uninstall a minute later. So it would be highly interesting to know what they were looking for. It could be helpful to add features to the app. Same is true if merchants uninstall after being a customer for a long time. I think a simple questionnaire after the merchant clicked uninstall, with multiple choice for reasons and a text box for comments should do it. Information is then to be displayed in the developer's dashboard.
I think it would be a very simple, but extremely useful feature for us developers. Some other features that were recently introduced (charts for installs etc.) are not so relevant.