I disagree that BTC is widely price against ETH. I would confidently assert at least 100x more BTC market participants care about the USD denomination rather than the ETH denomination. 

I agree BTC is the only reason ETH exists.

I disagree ETHs ENTIRE purpose is to add liquidity. Market makers are widely supplying liquidity with dollars much more.

ETH was created because people wanted a token attached to a blockchain with much more computation and smart contract features than BTC offers. Also they likely wanted to stack more USD with their pre mined allocations.