Back in Print
Unfortunately, the realities of the contemporary publishing industry are such that even books which are classics in their field, and which are often required reading for college courses, can go out of print. While ideally it would be nice to see such books released as open-source online books, the original electronic manuscripts (if they ever existed) for many such older books no longer exist. This means that putting them online or using some print-to-order service would require re-scanning the book, which can be prohibitive. So it is nice to see that at few classics in linguistic anthropology have reappeared, including Schieffelin’s The Give and Take of Everyday Life, and Sherzer’s Kuna Ways of Speaking.
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An anthropologist and documentary filmmaker, 
A properly managed scanning operation (like Google Print’s library initiative) imposes relatively little cost per work scanned.
The discussion on the Google Weblog
estimates a cost of $10/book, which is reasonable given my limited experience with such efforts.
I notice that the re-issued classics that you cite more than twice this amount per copy.
So there might be valid reasons not to re-issue such classics in digital form under some sort of Creative Commons license, but “prohibitive” cost is surely not one of them.