What sci-fi books are missing something that seems obvious to us today (and is somewhat central to the story / setting)?

My first thought was Dune with the ban on thinking machines. If you asked just about anyone today they would say the far future would involve computers everywhere. But Frank Herbert wrote Dune in 1965 when computers were huge, specialized machines and we hadn’t even landed on the moon yet. And he saw a future where not only computers became ubiquitous but we’re then rejected.

So what books jump out as missing something that we would find inconceivable today?