I may have been too hasty when I praised Left Coast Press for reprinting some out-of-print archaeology books from Academic Press. While some of these books are still valuable today, I can't see why whey would reprint an out-of-date textbook in Mesoamerican archaeology. Muriel Porter Weaver's The Aztecs, Maya, and their Predecessors went through three editions up through 1993, and it was the standard textbook during its time. But since 1993 the field has expanded greatly, there is an explosion of new materials and interpretations, and our understanding of ancient Mesoamerican has shifted in many ways.
In 2004, Susan Evans published Ancient Mexico and Central America, an authoritative, up-t0-date, and VERY well illstrated textbook (Thames and Hudson). This immediately became the basic textbook in the field, and it has remained so. A second edition appeared in 2008. So who would want to read Weaver's 1993 textbook today? No responsible instructor would assign this book (especially given its price tag, $70).
Well, I guess this isn't as bad as Dover reprinting Spinden's 1922 textbook (Ancient Civilizations of Mexico and Central America) in 1999. You would think that someone at Dover would realize that the field had changed in 77 years. The historical value of Spinden's text is not particularly high, either.
Basically, I have no idea why publishers would reprint outdated textbooks. But then if some publishers will take Wikipedia articles about ancient Egypt, put them into book format, and sell it on Amazon.com, I guess republishing an outdated textbook doesn't sound quite so bad.