Strava overtly markets itself as a social network. It doesn't open with, "use me - I'm an app to help you track your workout plan", it opens with, "use me - I'll share your workouts with your friends." The sharing of data is the primary feature and it's right there in the title of their website. If you use the app and think sharing is an anti-pattern, I'm concerned about your presence near nuclear weapons for reasons other than privacy.