OK you seem a little confused here? Like, first:
>that's the only example of a working and commercially available data-carrying optical cable that I know of
????? What exactly do you think every single optical fiber on the planet is carrying if not data? What do you think is special about the bits and bytes going over TCP/IP or FibreChannel or whatever vs Thunderbolt? Data is data. The cables I linked will do 2-10x the bandwidth of that Thunderbolt 3 one.
Second, the whole problem with that TB3 cable is that it has to go back to copper at each end, so it carries an active chipset and low volume transceiver in there to translate. It's not the optical part that is causing trouble, quite the contrary it's massively cheaper than copper. It's the legacy copper part that's hurting plus just plain Thunderbolt still being relatively niche, high end and until fairly recently still very restricted and proprietary, which resulted in an effective monopoly for Corning and ludicrous profit margin in turn. What I was lamenting in my original post is that the native connectors on boards didn't move to optical for data long ago. A 40 gigabit standalone transceiver like this [0] is $39 right now. It could be even cheaper if it was integrated on standard motherboards like USB or whatever else, both because of sheer economies of scale there is a lot of supporting material and such there going into that which could be done away with if modularity didn't matter. And after that you get to go up to 450' (or further with single mode at more cost). 100' costs another $39. 100 gigabit transceivers currently start at ~$100 for 100 meters, or thousands of meters for $190.
Obviously none of these carry power (though that can be an advantage in some cases where power fluctuations might be a concern), but it'd be trivial to make a cable with a couple of plain conductors along with it. If all they need to do is carry power and no data it'd still be very cheap. Data transfer is also much more efficient over optical vs copper, saving power and in turn heat.
And optical easily scales not just in cost but in bandwidth as technology evolves without needing to buy new cables. OM3 was standardized in ISO-11801:2002, so twenty years ago. If you got an OM3 fiber cable back when they first came out, that exact same cable would still be perfectly functional and useful to carry 100 gigabits for hundreds of feet right now, which wasn't even defined in 802.3 for nearly another decade afterwards. Can't exactly say the same thing about 20 year old copper cables.
Of course that isn't the way the world went for a variety of reasons. But it's a real shame.
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0: https://www.fs.com/products/36157.html