Definitely because it was faster. Amazon's strategy is to launch new features ASAP and then rely on everyone having to be on-call to fix shit when it inevitably breaks in prod because they rushed to launch. I will admit that while their "operational excellence" is shit, the security engineers do have quite a bit of power to block launches so their security isn't as bad as the reliability.
However, the fact that writes aren't horizontally scalable makes it a laughable nosql database but it probably satisfies the checkmark for enough of their enterprise customers that it will be a mild success and they'll keep it on life support like simpledb forever until they implement a proper solution assuming there is enough demand for it.
However, the fact that writes aren't horizontally scalable makes it a laughable nosql database but it probably satisfies the checkmark for enough of their enterprise customers that it will be a mild success and they'll keep it on life support like simpledb forever until they implement a proper solution assuming there is enough demand for it.