Comment by labcomputer

> What am I missing?

Not much, but consider latency: You can use the Group Execute Trigger (GET) to simultaneously trigger multiple instruments with both very low latency and very low latency dispersion. Think, easy-to-use sub-microsecond synchronization.

Ethernet and USB 4 may have orders of magnitude more bandwidth, but can’t achieve the same multi-device synchronization capability without side channel signals.

Now, sure, you can add the same capability with a programmable pulse generator connected via coax to the trigger input of all your instruments, but GBIP lets you do that with just the data connection (and you don’t always have a spare trigger channel). The only other protocols I know of with similar capabilities are PXI and PXIe, which are “PCI(express) in an incompatible form-factor, plus some extra signals for real time synchronization”.