Why doesn't heart rate get sent to Strava?

We don't send your heart rate data to Strava because it doesn't get sent to our server. 

We don't collect and store it, so it doesn't leave your device nor Apple Health - we just display the data the Apple Watch sends us. For that reason we can't send it to Strava, to be able to send data to Strava it needs to go to our server first.

We are aware that there is increasing demand for this though, so we are keeping it in mind as we work on further development.