My theory on the GPU miner is, that someone that would be motivated enough to have develop the gpu miner config, would probably have a lot more hash coming towards the pool.
Nice theory but in practice you can find a few guys... even on this own forum... able to write a miner but with limited hardware. Besides, it is relatively easy to spread the hashes to multiple pools if needed, a thing I would do if I had to GPU-port this algo.
Following for developments.