Here is my take on why ski videos themselves are not doing as well. And I swear to god, I am not trying to sound like a hater here.
Snowboarding.
Now hear me out, Back when Miller films were hugely popular, snowboarding was very, very new still, and very few people were doing it. Back then if you were into snow sports, you were a skiier pretty much. Once snowboarding got popular, it divided the audience for things like major productions. No longer did the snowboarders want to watch an all ski video that featured little to no snowboarding, and the same went for skiiers. Skiiers are generally uninterested in watching snowboarding videos. You are speaking of all of these major video companies, you are leaving out the snowboarding ones. I cant personally think of any, but I am sure there are companies in the snowboarding sphere that are equivalent to Stept or Level 1.
To compound this problem, it seems to me like when snowboarding first hit the scene it sucked out alot of the more 'extreme' talent. If you asked pretty much anyone on a mountain from the late 90s to a few years ago (or possibly still) what the public at larg perceived as cooler, I am betting the large majority of answers would be snowboarding (again, I have no evidence other than personal experience on this, so I could be wrong). This still seems to be the case today. As a ski instructor, I teach alot of little kids, and adults. The age bracket from 13 to say, 20 for someone who has never skiied, or snowboarded, much more often starts snowboarding.
Also props to someone assuming NS is not all 13 year olds. I love these kind of discussions and think they are great. And like it or not, WE (the 20-30) crowd, are the future of skiing. We will be the ones running the major companies and resorts in the next 20 years, and it is up to us to fix this problem.
In my opinion, skiing is still very often viewed as much less cool than snowboarding. We need to get that opinion back on our side, or at least back to a neutral point. It doesn't help that, at least at my mountain, there are about 5 ski instructors who are under 30 (and only 2 who are into park), and about 50 who are over 30, where as the breakdown for the snowboard instructors is exactly the opposite. 3 instructors over 30 teaching snowboarding, and 40+ under 30 teaching it.
Sorry about the wall-o-txt
TL:DR version, Snowboarders did it