Apple Watch VO2 Max.

Why does the VO2 Max only work on walks or runs in the fitness app? I ride a bike 3-5 times a week and would really want to see my estimated VO2 Max after these workouts. Results from a brisk walk or run won’t translate to my cycling because I’m not a runner. Is there any way it could or will there be a way that the Apple Watch could log VO2 with other workouts or even other workout apps (ex: Strava)?