Yeah, a lot of it comes down to network effects. Studios have to ramp up staff quickly, so they need to be able to find freelancers that already know the software they are using. So the studios have to use the "industry standard" software, unless they want to train artists, which wouldn't make sense since they are constantly ramping up and down their freelancer workforce. The Foundry (makers of Nuke) are surely making a tidy sum off of this situation.