I’m wondering how that is a question,haha. When it’s done for slo mo shots in videos,it’s done to throw dirt and look cool. When I see it on a trail where there is no need,I always just figure someone is playing around. When I see skid marks in front of a ledge drop,I know someone reconsidered at the last minute,or was not aware of the upcoming feature.
I think if you’re in control of the bike, there is no reason to lock the brakes up 98% of the time.