With restrictions on WhatsApp and Messenger audio/video calling features in some countries, imo is one of the best alternative to talk or connect with your friends over internet for free.
Sometimes you do not have access to good internet connection. Imagine you are in remote area with 2G internet connectivity. In such a scenario, it will be very difficult to browse Facebook through web on your Windows laptop. Facebook Lite for PC is app that will help keep you connected to your friends and family in that situation.