They might initiate some social events, asking you to join them so and so. Might be good if you normally play days the same way and forget to visit community lots etc. At the other hand, those incoming calls can be a bit annoying at times. Most of my sims have very few friends, that's because the game seems to prefer randomness. It doesn't matter who my sim hang out with, in a few days the friendship will be gone anyway. And suddenly there are a couple new friends - or enemies, that I never asked for. I wish this randomness would stop.