Whatever the degree to which these errors are purposeful vs. accidental (a distinction I think can actually be hard to make when you consider how thoroughly and subtly people deceive themselves), remember that it's a hell of a lot easier to improve the statistics education of the researchers than their ethics. And improving their education for some of these simple ideas can be at least as effective; if it's obvious to everyone what the correct statistical technique is (because they've all been a bit better educated), then such papers won't be able to be published with these errors.