This is a crucial distinction between gas-phase chemistry and materials physics and chemistry. For those with access to significant computing resources, exact exchange is not prohibitive for the comparatively small number of calculations needed to study an isolated molecule of up to a few hundred atoms. But that is manifestly not true for ab initio molecular dynamics (AIMD) of several thousand molecular-dynamics (MD) steps used to screen tens of different but kindred condensed-phase systems, for each of which the constituents are molecules with 300 or more nonhydrogen atoms. This distinction illustrates the compelling importance of continued effort to improve lower-rung DFAs. It also is but one example that there is more than gas-phase chemistry at stake in the development of DFT methodology and algorithms.