I use the social features very little; there are a few friends around the world I stay in touch with, with kudos and comments. I use segments to track progress on workouts and like Strava simply because of the sheer size of the leaderboards. It's a great motivator to not just see the numbers improve (for example time or avg power for a hill sprint), but also moving up the leaderboards. That's pretty easy when there are 70000 best efforts for a particular climb and even improving by 5 seconds lets you move up 100+ positions.