I wondered about this with automatic workout tracking. I walk to work as well (at least on the days I don't bike), and I don't consider it a workout... even though it's about 1.25 miles up and down hills steep enough to get my heart rate up. So I suppose one might consider it a workout, but to me it's just normal activity in my daily routine.
Same with bike rides. The majority of my rides are simply going to and from work (again... just over a mile and hills steep enough to get my heart rate going). I use an app on my phone call Ride Report that automatically tracks bike rides, but I configured it to not count those trips as workouts. I only record a workout when I'm going out for a long bike ride or walk for the purpose of getting exercise.
I guess it comes down to why you want to record your workouts and other periods of active movement with increased heart rate. If you want more details about the activity you get every day (more detail than just what the activity rings, step count, etc. provide), just let it record everything. If you want to reduce the clutter and see metrics only for actual workouts, it will be easier to monitor the progress of your training.