Jim Starkey, a Senior Software Architect for MySQL, said,
what a bother mapping back and forth between fixed-length declaration and variable-length storage! If the Standard would let us, the user could just say, "It’s a number—Just deal with it." Modern languages and frameworks have strings without size. Why not databases?
So that’s how I prefer to deal with ease-of-use versus performance: Make it easy for the user to let the software do the smart thing.
(…)
We’ll change the data model, the data types, the application topology, and the network interface, but they’ll still be relational databases.