I wonder why that is. My guess is that most amateur filmmakers would jump on exactly this kind of drone. Are there technical limitations that make a cheap(ish) version of that impossible? I don't know much about this, is adding a 150g gopro to a quad too heavy? Sure, you won't get any camera movement but you got more control than taping your gopro to a kite... Honestly tho, I watch a lot of youtube and 10 minutes drone videos are incredibly boring. I've never made it to the end of a single one. Maybe a 3h compilation over a good playlist to put on at a party would be a different story.The "I want to slap my existing gopro into an existing quad" market segment is kind of the worst spot in all of quadcopterdom.
Because if you have the first inkling of what you're doing, you recognize that a quadcopter gives you x,y,z... and for cinematography, you need x,y,z,P,T,Z,F (pan, tilt, zoom, focus). And if you don't care, you'll still recognize that more than 3/4ths of the weight of a GoPro is in its survivability. You can simplify the hell out of things by going with a lightweight camera built into the drone itself. The majority of the commercial drone work being done right now is realtor shots.