Big difference between audio and film both in how you restore them...
and how much it costs to do it.
First to restore audio you are primarily dealing witn re-recording,
scratch removal, etc. All things you must also do to restore a
film.... but a film also requires very expensive photo-chemical lab
work, pulling together various elements from all over the world, etc.
Much of what is considered "restored" is NOT but merely a video
transfer with some clean up so that the DVD will look good. To do
true preservation you MUST produce new film elements. As a
example.... all you L&H fans might want to ask if the silents have
been preserved for gnerations to come or merely just cleaned up on
video for immediate exploitation. If ony "restored" to a video format
what happens when the next format not compatible with the last comes
along.... will there be source material to go to?
Again about PD films.... yes if you want to get them out and seen
then, of course, the PD status is desirable. But if you want them
preserved then it gets a bit more iffy. Even if something is PD if
someone has really good pre-print they are going to hold on to it so
they can directly profit from their owning the physical property.
Also on the downside if a film goes PD but its pre-print elements
remain with a studio it is often inaccessible or even destroyed...
where as if they own it they are more likely to exploit (meaning
making it available) it. There is no simply answer to whether a film
being or going PD is a good thing or a bad thing. But, if there were
no hitches, no road blocks...... then wouldn't all pre-1923 films now
know to exist be available?