[bestouff]

This is not completely true. You can use a generic kernel with a custom device tree.

The only problem is that distributions currently tend to package them together, but that shouldn't be obligatory.

[dezgeg]

You can't if the firmware provided DTB doesn't follow any upstream Linux approved bindings and instead uses some vendor kernel specific bindings.

[M95D]

Why would you combine mainline kernel with manufacturer device tree? Kernel includes its own device trees.

[bestouff]

(S)he has a point. Sometimes the vendor dtb is all you have.