> Why is it that closed source drivers are the norm rather than the exception for hardware companies?
Because when you want to depreciate your old hardware and want to push your customers to new one, open source driver that is maintained, or even worse, add features that should be exclusive to your new hardware, you have a problem. Planned obsolescence is the name of the game in modern hardware industry. And even "open source" drivers like mwlwifi show similar pattern, good look fixing their ¢¢^√°^¢^° firmware.
Also when you depend on driver to differentiate between high/low end devices, open source driver is also no. Eg. Nvidia, throttling consumer devices in favour of enterprise grade ones.
Has this changed in recent years? Back in the days the consumer devices were faster but less reliable ( noone cares if two or three pixels are off in a 3d game). Cards based on the same hardware sold to industrial customers were just from better silicon bins run more conservatively. If you're running serious simulations you want accurate, reproducible results. Otoh, aerodynamic and seismic simulations can also be one or two "pixels off" and industry started to realize they can get faster equipment for cheaper by buying consumer grade...
This was all ~10 years ago, though, I think nowadays they just fleece everyone.
Because when you want to depreciate your old hardware and want to push your customers to new one, open source driver that is maintained, or even worse, add features that should be exclusive to your new hardware, you have a problem. Planned obsolescence is the name of the game in modern hardware industry. And even "open source" drivers like mwlwifi show similar pattern, good look fixing their ¢¢^√°^¢^° firmware.