If your database lives past infancy, and is deployed into a production environment and starts accumulating sizable amounts of data and users, sooner or later you will begin to worry about whether it performs at the optimal level. Being able to tell the RDBMS what you need is one thing, making sure that your order is executed in the most efficient way is another. The SQL is very good in abstracting your data needs from actual execution; all you need to say is what and let the RDBMS figure out how.
As your comfort level with the language grows, and you gain more knowledge into the relational databases world, you might begin to question the authority. Why does it take so long? Are my queries executing at the “as good as it gets” level, or are there ways to speed them up? Does my database perform at optimal level?
These and many more questions are bound to pop up should you stay in SQL land long enough.