It is a given that applications must provide users with the functionality necessary to accomplish some task or goal. The effectiveness of app functionality is the first determinate of how users perceive the apps they use. However, it is not the only thing that influences user satisfaction.
The User Interface and User Experience (UI/UX) features developers build into apps have at least an equal amount of influence on users perception of an app. It may be an oversimplification, but UI/UX is largely (but not wholly) concerned with an apps "form". Personalization is an aspect of UX that tailors characteristics and actions to the individual user. Personalizing app functionality in this manner works to make the app easier and more pleasing to use.
The objective of the Hello app is to leverage geolocation to obtain the users country so it can then generate a customized greeting in the users native language.