I used, for my sins, design books (including covers) for academic publishers. I just scrolled back in time and some of them weren't half bad. I'm not sure why we put much effort into the covers they were mostly assigned course materials. That said, a lot of effort went into the innards. I used to quite enjoy it, but it didn't pay very much (not as much as Tidy Haired Thought Leadership™ and drawing kittens with lines). I doubt many people realise the mental perspiration that goes into these things.