Perhaps this has something to do with the "real world". . . And to make it clear: wave-function-based theory should be used wherever it can be used. But this is exactly the point. DFT is applied for large systems because of its low computational scaling law, O(n 3 ), with the number of particles involved n, and where wave-function-based theory has (and in future will still have) real problems -for example, in describing electron correlation for strongly correlated and metallic systems. The electron-correlation problem for metallic systems in wave-function-based theory was already pointed out in early days by Fulde 466 . Here, DFT gave us many useful results of the "real world" where ab initio theory is just not able (yet) to do the same job. It has become therefore an invaluable tool for materials science, solid-state physics, and the simulation of biomolecules.