If it's presented as an archival project (like Project Gutenberg), it seems like it's performing a public service. It's when people are less clear about it that it seems spammy: you're republishing a 1903 cookbook, but not being very clear about the fact that that's what you're doing.
Even worse, and not really performing a public service, is when it's republishing old content that someone else has already digitized, like the dozens of sites republishing Project Gutenberg books with no real value-add.
Even worse, and not really performing a public service, is when it's republishing old content that someone else has already digitized, like the dozens of sites republishing Project Gutenberg books with no real value-add.