Are these big "dominant" institutions charging for this data? No, the spend a lot of resources putting them together and give them away free.
Are they preventing others from giving away data? No, but it costs a lot and they bear that cost.
Are they forcing smaller institutions to use their data? No. Its just a free resource they offer.
Do they get the grants themselves because they have some kind of proprietary access? No, the whole point is that the benchmark is open and everyone has access.
So they collect this data, vet it, propose their use for benchmarks and give it away free. What is the complaint? The problem is not even posed as "well, this data is overfitted in papers or we are solving narrower problems". [Edit: they sort of do, but leaving this here so the comment below makes sense as a follow up.]
No the complaint is that these handful of institutions are giving away free data so too many people use it? Can we have more "problems" of this nature?