I think oz2cpu's point is that the problem is still easier if all the necessary hardware and software is contained in a single box, rather than if you need to get the instrument, cable, computer, software, etc all from different sources, and inevitably separated from each other over time. Bonus points if the software has some annoying copy-protection like a hardware dongle or online activation. If the PC is embedded in the instrument, like modern high-end scopes, then at least it will stay with the instrument over its life. But if you don't even have the software, and the instrument is fully reliant on that software to do anything useful, then it's game over for that instrument.
For DMMs: Keysight/HP/Agilent, Rohde&Schwarz, Siglent, Rigol, Keithley, Tektronix, ...
For Scopes: Keysight/HP/Agilent, Rohde&Schwarz, Siglent, Rigol, Keithley, Tektronix, LeCroy, ...
For Signal Generators: Keysight/HP/Agilent, Rohde&Schwarz, Siglent, Rigol, Keithley, Tektronix, ...
How many DMMs and signal generators do Tektronix, Rigol and Siglent make that rely on PC-control? How many scopes and signal generators does Keithley make at all?
list may be continued. All of them now offer remote-only instruments. The market is clearly automated testing
in a factory environment, and this market is huge. Here you need the max of test functionality in a cramped space. All this PXI stuff is just doing that.
Sure, this has been going on for decades. NI has been doing that or a long time, but their hardware is generally very reliant on their software. Can you talk to PXI devices without any instrument-specific driver, like a stand-alone scope that supports LAN and SCPI over TCP/IP? Is for example the R&S PXI line SCPI? The only thing I find in their documentation is how to use their drivers, which will no doubt stop working at some future Windows / LabView update.