Try to write some GPU software on AMD cards, then compare that to the NVidia/CUDA experience. I don't know about the Bitcoin thing (maybe in the end, for very long lived code, the lower cost would be more important than the developer pain and time time required) but for pretty much all the HPC code I see, getting things running sooner and with more polished dev tools beats price/performance ratios every time. If you're spending a few thousand on Titans anyway, getting a few more cycles per watt doesn't matter all that much anymore; except for Bitcoin mining where your main cost is energy (by design).

So I think there's a very clear reason for that specific case.