They didn't list them, but they said quite explicitly:
IWI and myself spoke to most of the major studios
in the U.S. and Europe. We spoke to 8 out of the 10
most famous studios out there.
By studios I assume they actually mean publishers, who control the copyright. The huge ones. They admitted, DRM is pointless:
We met lots of interesting studio executives, who
totally understood our pragmatic arguments. Many of them
even admitted that there is no DRM that can prevent a
title from being pirated and that some of their movies
sometimes even got pirated before release, just like
games unfortunately.
But failed to do anything about it:
We even got one offer approved by the business folks of a
major studio, but the deal eventually got cancelled
because lawyers were worried that it would give the
impression that majors are giving up the fight agains
piracy.
Also, most of the major studios told us, each with
almost the very same words: "we like your ideas, but
we neither want to the first studio to say yes, nor the
last one. Please let us know when one of the other major
studios says yes, we will then probably consider
following".
> Many of them
> even admitted that there is no DRM that can prevent a
> title from being pirated and that some of their movies
> sometimes even got pirated before release, just like
> games unfortunately.
I don't see that as being indicative of anything. They were only pitching to release classics, and even then, only 1 studio was willing to sign up. The most optimistic interpretation of this is that studios are okay with DRM-free releases for their classics, but not for their newly released blockbusters.
Whether you see that or not, the market is not addressed, whether because of fear of doing something first or simply backward thinking mentality of lawyers and others in that mostly legacy industry.
I.e. instead of selling video DRM-free, they are losing sales to piracy which provides these DRM-free options already. Smarter execs would have started competing by providing legal DRM-free buying options. Whether it's recent blockbusters or old classics is irrelevant. The issue applies to both equally.
The reason GOG started with classics when addressing these execs, is to have easier time overcoming common stereotypes and fears. Not because DRM-free is only relevant for classics. What they discovered is that even with classics, the backwards thinking is too entrenched there.
What are those "major film publishers"? All the movies in your link are niche.