A couple years into my career as a trade author, I got really irritated that my publisher was keeping a competing how-to book in print that was really bad. I don't mean it was badly written, apparently it was good enough to have sold over 100,000 copies in its heyday. The problem was that it had become obsolete. It was so obsolete that you could not buy the parts needed to carry out the instructions, and they weren't applicable to the newer generation of technology. Yet, the publisher continued printing the book, the bookstores kept on ordering it, and customers kept on buying it.
The simple answer is that customers kept buying the book, so bookstores kept reordering and so the publisher kept reprinting. Unfortunately, the customer was making a mistake, the bookstore was making a mistake and the publisher was making a mistake. The customer, either a budding hobbyist or a parent, can hardly be blamed for buying a basic how-to book that's obsolete. If the budding hobbyist knew enough about the technology to realize that the book was obsolete, the hobbyist wouldn't need the book. Parents have even less ability to judge the suitability of a book for a hobby that isn't even theirs. All these first time buyers have to go on is the appearance, the price, and the fact that the bookstore has the book on the shelf.
Bookstores buyers can't be expected to be experts on every genre of how-to book they carry. All they know is whether or not the book sells and whether or not it gets returned. Most people aren't going to bring back a book that they've bent up, read, and thrown on the floor, not to mention the tear stains. The store buyers see the book is selling, and don't know why a book about technology X shouldn't have the same shelf life as a book about technology Y. Take the example of computers vs squirrel-proof bird feeders. Anybody familiar with the subjects could tell you that squirrels are constantly evolving. And it's not a matter of years in print or the copyright date, some books are obsolete when published. New books that are up-to-date can last six months or six years, but the borderline is usually sharper than non-technical people may expect.
Normally, I'd be happy to blame the publisher, since they are generally in a position to know that they are selling obsolete books. However, with all of the personnel turn-over at the editorial level, it is possible for publishers to lose the internal expertise, such as it is, to realize that they are pushing toilet paper. There's also the problem of the bottom line. For a publisher to declare a title out-of-print while it's still selling through and no replacement is available is a bit of a stretch. Besides, due to differences in the approach and layout of the obsolete title and my title, I don't think the publisher groked that mine was a replacement. The obsolete title continued selling for years before a new edition was finally produced, which they promptly wrapped in "my" cover.
Of all the things that have annoyed me about trade publishers over the years, reprinting and selling obsolete books is the one that hits me in the gut. It's probably because I have memories of buying books as a child and being terribly unhappy, though not because they were obsolete. I'll bet that hundreds of thousands of obsolete or plain useless how-to books are sold every year, and that it many cases, it will be the last how-to book that person buys. But worse than the permanent alienation of customers are all the tearful children and sheepish parents, who in their confusion, yell at their poor kids to "do it anyway."