Do you log your training? How? Why?

Whilst many of my running friends are on Strava, use a GPS watch or log their training somehow, some do not record their training.

I am keen to know if / how / why runners log their training. The survey takes less than 30 seconds. I would be most grateful if you could click the link and answer the three multiple choice questions.
Many thanks in advance!

https://www.surveymonkey.com/r/YK9G7VS

Strava

Strava – Syncs with your GPS watch, or you can run the app on your phone. A social site you can share your workouts and races on. Great to see how your training compares to your friends. Strava has a match your run feature allowing you to see how you have improved since you last ran that route. There are segments created (you can add your own) which let you compare your efforts with everyone else who has run that segment, this might be up a local hill, or a loop of the block.