Fear of missing out on market segment, as well as support for super-computer configurations. Without keeping a foot in the door for these segments, they risk fading away into obscurity like 3dfx did back in the days (for other reasons, however).

For perspective, 3dfx had stellar drivers for their cards, and never had issues with linux kernel maintainers refusing merges of their code for lack of quality.

> some value

I think you have answered your own question here :)