The central locus of study of computer science shifts depending upon what real computers do. We care about parallel and distributed algorithms more because we

The central locus of study of computer science shifts depending upon what real computers do. We care about parallel and distributed algorithms more because we have real parallel machines and big distributed systems of many machines. It's not an obscure graduate offshoot about future hypotheticals and exotic high-end machines. We care about cache efficiency and memory access efficiency a whole lot more, because the ratio of speeds in a typical computer has changed. And we're not spending so much of our time studying n-way tape merges anymore... even though they may come "back" because of these shifting constraints. Real changes in what's typically limiting and what we're trying to do with computers shift the emphasis of computer science around. And the tick-tock cadence between individual resources and centralized resources... across scaling horizontally and scaling vertically... between single fast machines and distributed systems... can be expected to continue.