Question about Ethereum use. 2nd question.

I have a question about current Ethereum use. Specifically, what actual businesses are using the Ethereum blockchain right now. I tried to look for an answer online, but once you use the word business and blockchain the web spits back a million web responses about companies that are using, or are about to use blockchain tech. Some are even lists of companies that included one that had a list of 81 of the top 100 corporations.

Here's the snag: I can't find what companies are actually plugged-in to the Ethereum blockchain. They all say that they have spent 'X' amount of dollars changing their models to blockchain, but when I looked further it seemed like they just used their own blockchain. Either they created it themselves, or they just cut-and-pasted the opensource blockchain code from somewhere else.

What is the incentive for companies to eventually use the Ethereum blockchain? If Google, for instance, or Walmart create their own blockchain and use it, is there a reason that they would plug-in to the Ethereum one? What is their incentive?

I can see where I wouldn't trust any company I invested in, especially banks, as far as I could throw them. I would absolutely want anything 'verified' by Wells Fargo; Goldman's, etc. to be verified by the Ethereum blockchain. Is that part of the usage plan?

I tend to drone on a bit, so I'll just boil it down to: What companies will be using the Ethereum blockchain. If not, who pay for all the mining? I think I read other coins use the Ethereum chain, but are they used by real world companies, so are they, by default, used by actual businesses?

Thanks in advance.