Because radlibs looking to be more revolutionary than they are feel safe adopting Anarchistic labels and some leftist language. Generally speaking, only people who have really read, understand, and internalize the literature call themselves a ML, not because ML's are somehow superior but because they are "The Bad Guys." On the other hand any Radlib can read the introduction to the Bread book, or whatever Anarchist text they havent actually read, and claim to be an Anarchist.