Now compare with Franchise, Jokester, All the Troubles of the World, The Last Question and many more stories that feature as a plot device a very powerful centralized computer named Multivac. (See https://en.wikipedia.org/wiki/Multivac for a more complete list.)
How the same mind could have come up with the idea of androids with positron brains following the three laws of robotics, and yet missed pocket calculators baffles me.
In many ways we're doing that exact thing. The computer at my desk is powerful but somewhat useless; the grand oracle in the form of Google et. al. does the real heavy lifting of giving me useful information. Whether it's a single computer or a bunch of separate ones acting as a whole is pretty immaterial in that sense.
It is called a paradox because seeing it in action usually catches people by surprise. And this is true whether you're talking about the consumption of coal to power factories, or the consumption of electricity to power computing (and in each case the myriad of new uses that efficiency promoted).
In Science Fiction over and over again the trope was of a giant computer that acted like an oracle. You see that in Asimov's work, in Heinlein's The Moon is a Harsh Mistress and so on. Basically nobody anticipated ubiquitous computing. For instance in the Foundation series you see that a computer run by the Second Foundation can predict the future course of history...and people are calculating their courses with slide rules.
As for the killer app of computing, email, I'm only aware of one pre-1970 work correctly anticipating what it would be actually like. (James H. Schmitz has a memorable scene in one of his Telzy stories where she catches up on her messages at a terminal. He doesn't say "email", but the scene is notable for unobtrusively getting it right.)