Faster communications over distance. Before phones there was only telegraphs and later telegrams (a bit like texting but you had to go a place that offered the service) and the US post mail which took days. Or if in your town you went to a persons house or got someone to take a message to them. Phones made communucation faster and more efficient, esp over distances.
the "real purpose" (and i mean the first phone actually made) of a phone it to talk to people that are far away from you and you can't get to them to talk personally. Nowadays, people text and play games and listen to music.