If you are building an app that has a social aspect to it, you have to make sure it is usable before it has enough users or content to be valuable as a social network.
For example, if it’s a dating app where users can contact each other, or a marketplace app where users go through lists of items posted by others, you have to make sure that the app is usable even before there are enough users to date, or enough marketplace items to scroll through.
Social apps have a “critical mass” aspect to them, which means that until there are enough users or content, they are useless. A user that opens an empty app and sees that he is alone or that there is no content, will most likely delete it or close it and never open it again. It is not reasonable to expect that someone will add his own profile and content, and then try the app again after a few days to see if there is more to do and others joined.
Don’t count on having a big launch where many users will join at once and start interacting with each other right away. Instead, when you design such an app, make sure to higlight other functionality until you get that critical mass of users or content that you need.