Ben Harris' expresses a view that gets aired on an infrequent basis; that changes in technology may signal the death knell of some branch or other (or force some Darwinistic survival mechanism...).
The same thing has been said in the past in regard to stage illusions losing their impact due to advances in movie special effects (ie; audiences will be underwhelmed because they can see ANYTHING on the silver screen). This view was often expressed prior to the golden age of the stage show in Las Vegas so, in hindsight, we know the scenario never eventuated.
I think Ben is right in expressing the view that coins will one day be obsolete in fiscal terms - and that this may affect their relevance as a prop. Darwin Ortiz makes the same point in Strong Magic when he observes that the Miser's Dream is no longer an effect that delivers a wish fulfillment to the audience - that is, the desirable ability to comb the aerial mint, and to thus never be poor again. These days it might be better to produce American Express cards...
But people will always appreciate the concrete nature of a coin - that beyond chemistry (alchemy?) and perhaps super human strength, a coin can be relied upon to retain it's form. People know this in their bones. Therefore all of the effects involving transpositions and transformations, or gag effects where you bend or pierce a coin, will always remain effective. Even if a spectator had never seen a coin in their life, they would soon be convinced of these qualities after a cursory examination, "Here, this is a silver dollar, it used to be currency way back before credit accounts were part of our genetic coding..."
I think that the main reason that published coin effects are outnumbered by card effects is that the creative possibilities are more limited or alternatively (and less likely in my view) that while possibilities might be endless it is more difficult for most of us to conjure up those possibilities. That's why the majority of coin tricks are quick and visual and follow a limited range of archetypes.
The same can be said for dice. Most Australians gamble on slots, horses or cards - but they still know what dice are when they see them. I'd love to have more material related to dice to perform but, like coins, the physical prop only offers a limited range of effects and methods: transpositions, colour, size and spot changes, predictions, and the uncanny ability to control fate and fortune.
Another reason why there are more card tricks in print is that there is a very short start up time for the budding creator. I mean that a lot of people are creating and writing up variations on the simple tricks they have started to learn before they've mastered a greater range of material. This would explain why there are so many bad sandwich effects around - they are just about the easiest card effect to devise. (That is not to say there aren't GREAT sandwich methods out there - Roy Walton's "Smiling Mule" , Larry Jenning's and Derek Dingle's "Visitor" type effects, Ben Harris' "Fandango" move, etc. But they are far outweighed by awful tricks.)
This is in contrast to coin magic where even the basic moves may require an investment of time to master that is beyond the pain threshold for most magicians. (I don't do coin magic but I do dice moves, so I know these things don't come easily.)
Anyway - enough rambling from me...