"there are lots of good free Linux drivers "
When you work with expensive hardware, you may care less about "good free drivers". You need vendor supported drivers because if your hardware doesn't work as expected, you call the technician and expect he brings it up to specs. You don't want an answer like "you're using it with unsupported software, goodbye".
And, no, you aren't going to fix it yourself because if you're an artist you may know nothing about drivers and kernels and compilers and whatever. Nor you will look some unknown stranger in a forum and pay him to fix it for you, without any warranty.
And it's not only the driver, but all the management and calibrations tools you need, which usually work very close to the drivers.
My monitor performs color calibration in hardware - it needs its software, and the spectrophotometer one, to be calibrated and load the calibration at startup. The printer has media management and accounting software, which are essential in a professional workflow.
When you are using several thousands dollars of equipment to deliver your products, the cost of the OS and the software is almost irrelevant. The costs of fighting with unsupported software could be much higher.
When it is no longer supported by your OS, probably you have already used it enough it's time to replace it anyway, if you didn't already.