Sometimes when we’re writing sf we have to stop and think—why are my characters using tablety projector things instead of having images imprinted digitally in their vision—or something like that.
Technology cropping up that would seem conspicuously absent in a futuristic universe is a common issue for science fiction writers—especially in a world where technological advances come quicker than the average novelist can crank out a fresh pile of steaming genius.
There are a lot of ways to address this issue: 1)you can give that technology to you characters and deal with the consequences
2)you can not give it to them and ignore the issue
3) you can explain why that technology never worked, OR
4)you can explain why that tech exists but nobody uses it.
The choice the author makes should depend on the story—what feels natural and what befits the plot. Every new piece of tech an author introduces will undoubtedly change the story—just think of how many old movies would fall apart if you gave all the characters cellphones (or if you don’t feel like thinking google it).
If you find that you cannot include the tech without destroying a beautiful and dramatic tale, I’m all for explaining it away (3or4). In some cases the explanations are more interesting than the tech itself—one of the better examples being D.F.W.’s explanation for the non-use of video phones in Infinite Jest.
There’s an added perk of picking option 4 (addressing the tech and then explaining why nobody uses it anymore), namely the author can still use that tech later in the story. Or, perhaps you could have one kookie character that still has rental implants and thinks they’re great despite the weird looks he gets when he interfaces with screens that only he can in the grocery store (much like people talking loudly into their Bluetooth earbuds).
Of course if you pick option 3 that sets up the possible discovery of the functional technology later in the story as either a legit bit of foreshadowing or to throw off your reader just a little bit (which all readers enjoy).
That’s where I’m at. Give me a couple years and you can read all about why people don’t wear digital contacts in Tinkertown. Until then feel free to share your favorite explained away bits of tech.