How animation in mobile apps helps retain users

Along with the features of the mobile app and the usefulness that it provides there are many other things that are highly effective when it comes to retain the users for a longer period of time. As time has passed developers have started using new and improved ways of retaining users. According to a professional and very experienced company for app development in California the use of animations in a mobile app helps to impact the mood of users in a very positive manner which helps the developers in retaining users for a much longer period of time. What other ways can developers use for retaining users?