Why did Amazon take so long to deliver SQL in the Cloud

The storage market has been complexifying, (Is that a word Ed.) over the last few years; I have for a while considered the databases to be just another software abstraction layer between the hardware and the application i.e. completely equivalent to a file system. Also more recently it is clear  that the highly scalable solutions builders have moved beyond relational databases. I conclude, today’s application designers and storage consumers are no longer always prepared to accept the compromises  buying an RDBMS requires, it’s about Storage not SQL. …