I'm still struggling to think of what drivers would actually count here, depending on what time period we're talking about. Early 80s? Late 80s (Win3)?. INT 21h file services?

It was the era when DOS games didn't use "video drivers", they all wrote directly to the VGA registers. Similarly for sound cards: you could buy a Soundblaster or (if you were rich enough) a Gravis Ultrasound, and other manufacturers cloned the hardware API directly. Games later tended to come with "DOS4GW", which was effectively a 32-bit operating system that could load from and return to DOS.

Essentially all 86/286 PC OSes have some level of compatibility with MS-DOS drivers (either because they are compatible reimplementations of DOS or CP/M derivates with some level of DOS compatibility).

Also for many hardware devices in DOS days there simply were no "drivers", but each program that wanted to use given piece of hardware had to communicate with said device directly.

DOS itself provided interface for block devices (with weird extension mechanism for things like ATAPI), semi-documented API for installable filesystems (meant for network drives, but also useful for ISO 9660), mostly unused abstraction for some character devices and print spooler which included exactly one printer driver (for some IBM printer that most people didn't even ever see).

The 32b windows VxD/WDM PnP model seems like perfect (and probably unintentional) marketing for MS, because it exposes the fact that there are drivers and that said drivers are not available for OS XYZ to the users, while it can be perfectly the case that there are no third party drivers for given device for OS XYZ because they are not needed (either OS XYZ already contains drivers for such device or the device simply implements some standard interface).