That's because it is top of the line and very few devices actually need that kind of bandwidth. For switch-to-switch links I can see the point (and for specialized datacenter applications) but for home use it is mostly overkill.

There are adapters from USB 4/Thunderbolt to 10 Gb/s Ethernet.

Moreover, when 2 computers are close enough, you can connect them with a Thunderbolt cable and you will have the equivalent of a fast Ethernet connection. The operating systems will show extra network interfaces that can be configured and used for communication between the two computers.

Now all new Intel and AMD low-power CPUs include a controller for two USB 4/Thunderbolt ports, so there are no good reasons for any new small computer or laptop to not have them.

If the USB 4/Thunderbolt ports are not occupied by a monitor or power supply, so both are free, you can daisy chain a large number of small computers in the equivalent of a 10 Gb/s Ethernet network, without expensive switches, adapters or NICs.

That's not what I want from a vendor. I want clarity.