Most of them are pretty obscure -- silent films, foreign films, or compilations.

Lili and The Magnificent Ambersons are the only ones I'd expect someone who's not a film buff to recognize. Possibly there have been rights issues that kept those two from being issued in DVD format. Or lack of interest, I suppose, but that seems unlikely given how many more obscure films have been released in DVD.

I think libraries (and interlibrary loan) are going to be my best bet.