I found two writers who commented on the issue, Ben Bova and Isaac Asimov, either or both could be repeating an insight he'd seen from someone else, so I'm not sure where it really originated, though I suspect Asimov since he repeated the comment in multiple works, and his is also the earliest example I could find.
In Ben Bova's 1981 book The High Road, I found this quote (in google books snippets here and here):
Jules Verne, H.G. Wells, Robert A. Heinlein—every major and most minor science fiction writers took a crack at the first-flight-to-the-Moon story. Not one of them predicted that the first lunar landing would be televised back to billions of eager watchers back on Earth.
And I found this metafilter thread where people thought it came from Asimov, I recall him commenting on this in some essay as well (and I hadn't read either of the two below). The earliest reference they were able to find was the essay "Our Future in Cosmos—Computers" which appeared in The Impact of Science on Society (1985), where he wrote:
Decades ago we science fiction writers foresaw a great many things about space travel, but two things we did not foresee. In all the time that I wrote stories about our first Moon landing and about the coming of television, nobody, it far as I know, in the pages of the science fiction magazines, combined the two. Nobody foresaw that when the first Moon landing took place, people on Earth would watch it on television. Nor did science fiction writers foresee that in taking ships out into space, they would depend quite so much on computers. The computerization of space flight was something that eluded them completely. So, I have two broad areas that I can discuss in talking about our destiny in the cosmos. One area is the future of computerization, and the other area is the future of space itself.
But I just found an earlier reference, in Asimov on Physics from 1976, where in this snippet he writes:
One thing that no science fiction writer visualized, however, as far as I know, was that the landings on the Moon would be watched by people on Earth by way of television.