I would say it’s a combination of the prices of 10GbE controllers being high, taking more resources and more die area to make and the latest chip shortages since the you know what that shall not be named.
Back in 2012 when 10G was hitting the mainstream (or that’s when I know it kinda did, my knowledge ain’t perfect), the power consumption on 10GBase-T was huge compared to fiber. So people tended to stay away from Ethernet, they went straight to fiber. But not everyone was happy with fiber, re-running cables is costly.
Later on, the 10GbE controllers got more practical, but by that time, we already developed NBase-T around 2016 and developed 2.5GbE controllers that are similar in size with 1Gbps controllers and use about the same power.
Additional reasons why 10GbE didn’t make it into mainstream was that, because of its larger size required on a PCB, device manufacturers just stayed on 1Gbps for a long time, delaying people from upgrading to fiber. By the time 10GbE NBase-T controller caught up with lower power consumption (about 7W, which is still massive compared to gigabit), it was already too late, most enterprise businesses already went to 40G and even 100G. Some cheaper 25G can be found today too. All of them use fiber.
10G was kinda plagued from the start. Not the fiber ones, but the copper ones, most early 10G were fiber, because they used less power and had other advantages, like longer wire runs.
Now, consumer devices are barely starting to see 2.5GbE hitting the mainstream because the consumer tech has advanced enough to allow those to be mass adopted. But many ISPs in countries that are not burgerland, are upgrading their residential customers to FTTH gigabit and preparing the infrastructure for future speeds, while ISPs over here are milking coaxial some more and some even DSL.
Considering the price of 10G today, I am gladly embracing 2.5GbE. While true that had the 2.5GbE tech not been developed, we may have seen 10G adoption earlier (probably non-RJ45). But the ethernet one would have been costly in the long run, because of its power consumption. You don’t want the climate to change, do you, anon?
As mentioned, I am in the market for a 2.5Gbps dual port PCI-E x1 or x4 Intel NIC. The i-225 is expensive at $100 and the x540 and x550 (the former which doesn’t even support NBase-T) are $300. And the newer x710 is $500 for a dual port, that is insane. So if anyone has any recommendation, let me know.