In reply to SouthernSteve:
I generally only join the run distance and climbing challenges but more as a way of easily seeing my monthly total at a glance rather than any real comparison, but it seems silly to remove this. Especially as there's no explanation as to why from what I can see.
I still love Strava and have been on it since about 2013 I think and was a premium member for a lot of that period, but I feel like they've squandered a lot of goodwill by resting on their laurels a bit (I refuse to pay for premium until there's a solid TrainingPeaks-style annual training planner available).
I guess a lot of their revenue stream now comes from selling data to cities and governments to plan infrastructure projects (which is a good idea IMHO) and sponsorship partnerships