The idea behind this is that every company buys their own Oracle-based grid. This means lots-of-money for them.
If everyone switches to "the cloud" with non-relational data stores, that's not so good for them. (Even if "the cloud" is Oracle-backed, they still only sell one copy.) They have made a lot of money convincing people that their product is magical, and they don't want to lose out on that.
You know, back in the day, Oracle did exactly the same thing themselves - they released their product on IBM mainframes because no-one would take them seriously otherwise. They even had to leverage a consulting contract with the CIA to claim to be "government contractors" to convince IBM to sell them ones.
By no means did they invent this strategy, nor are they the only ones to use it, they're not even the only database vendor. MySQL relies equally on "magic". Selling on your technological merits doesn't work. Look at Sybase and Informix.
Since when did the cloud mean non-relational data stores? For that matter, since when did the cloud mean anything concrete * ? I've heard cloud computing describe more ideas (all of them ancient) than almost any other term in computing. Yes, the cloud is yet another instance of "What's old is new again."
* other than "it's running on someone else's machine"
If everyone switches to "the cloud" with non-relational data stores, that's not so good for them. (Even if "the cloud" is Oracle-backed, they still only sell one copy.) They have made a lot of money convincing people that their product is magical, and they don't want to lose out on that.