As for 'other sources for classic film', as a TCM Insider (please don't hate me, I didn't volunteer for the role, just accepted it!), I was asked what other sources I had for classic film.
I mentioned MOVIE-TV, GET-TV and my local PBS. As for the 'why'; it was because they show studio-era films that TCM doesn't show. E.g. MOVIES-TV features a lot of 20th Century Fox films and GET-TV, Columbia films.
If TCM brass listens to so called insiders, maybe this will result in more films from studios (especially those outside the Turner library, like Monogram, Republic and United Artist).