They do pay for drivers and other engineering work. I don’t know how it is now but Canonical was in that business. As for why OEMs don’t do it more, or why the

They do pay for drivers and other engineering work. I don’t know how it is now but Canonical was in that business. As for why OEMs don’t do it more, or why they don’t do it instead of paying for Windows licences: custom dev, testing and certification for each model variant is a significant cost. Even if the OEM saves that money of Windows licences, the market mostly demands Windows. System76 is a company that produces laptops and desktops with their own custom Ubuntu variant, if you want to see an example of one company going the full Linux route.