Ekstrand: Introducing NVK

Leaving aside the philosophy there are cases where open drivers are a huge practical improvement.

All closed drivers have the problem of platform availability. If the vendor only provides it for X86 and you want to use ARM or RISC-V you're out of luck.
They also have no guaruntee of support over time. When you're putting an embedded device in the field and need to support it for 10 or 15 years this can be a big issue.

There can also be toolchain issues. For example distribution may require certain build time options and complain (or refuse to run) binaries that don't respect that. Eg a number of years ago Android switched to wanting all binaries to be built with -PIE for security reasons. This is problematic for anything that can't be rebuilt.

For a "standalone" driver, implementing a single known and mostly stable interface it may not seem that important being mostly a question of the number of bugs and the level of trust we can have without source code.

However graphics drivers are not standalone; there is a whole, very complicated, fast moving, stack stradling both kernel and userspace and including things like X and Wayland.
One huge problem with closed userspace graphics drivers is that the are written for a single stack (ie a given kernel driver and a given higher level userspace framework like X11, Wayland, Android, ...). This means that the closed driver is often useless to those who want to use it outside of its original context.

Closed source graphics driver also reinvent everything each time whereas the open source equivalents have lots of common code meaning that, once the hardware specific parts are done they all tend to advance together.