You still didnt answer my question though, there is no incentive for a corporation to connect to your nodes and use your tangle, instead of making their own.
This can be a general question for all cryptocurrencies such as bitocoin and ethereum. The main advantage for public crypto network like bitcoin, ethereum and iota is their lower cost and higher efficiency when comparing to their private counterparts. For instance, the payment/tansactional settlement cost and data storage cost can be much cheaper in a public network than a private network. The entry barrier in a public network is much lower than a private one. Lower cost and higher efficiency can be translated into profit which is the ultimate goal for the companies.
That is why many people believe that the private blockchain (blockchain/bitcoin without coins ) will not work because it will lose the advantage of lower cost. Whence a company loses the advantage of lower cost it will lose the competition in the marketplace. Maybe in the future the private chains and public chains will co-exist. But public chains will still be the dominant force in the market simply because they are cheaper and more efficient, maybe similar to today's internet and intranet.