Thank you for your suggestion to add motocross/dirtbike as a Sport Type. Your idea has been submitted to the team. Right now, we aren't exploring the possibility to add motorized sports on Strava. In the meantime, we invite you to explore the available sports types on our platform (more than 40 and counting). Thank you for being part of our community and we look forward to seeing you on Strava!"
You already have motorized sports on Strava. E-bikes and e-mtbs have motors! Not to mention that there are mx/trail and enduro bikes with e-motors.
In short, you don’t have to explore the possibility, you already did. Just have to add the activity.