Probably because of their age.
Try here:
Classic Collection DVDs : The Last Mile (1959 (http://www.classiccollectiondvds.com/product.sc%3Bjsessionid=D861E81571AA291B41A9842C57 ABECF9.qscstrfrnt02?categoryId=3&productId=72 - broken link)
Free Classic Movies on DVD - Home Page (Press CTRL and the F key to open the 'search' option. Type 'the last mile' and it jump to the listing at the bottom of the page.)
For Macabra, try this:
Welcome to RAREFLIXONDVD.COM: Mermaids of Tiburon (1962) DVD - SHANKS (1974) DVD : MACABRE (1958) William Castle (http://shop.rareflixondvd.com/product.sc?productId=5&categoryId=10 - broken link)
Hope that helps!