There was also a point where "internet scale" was impossible to handle on regular RDBMS's without massive amounts of pain. But disk IO performance has gone up dramatically since, and capacities likewise.

So a lot of caching that many of us had to do to scale systems a decade or two ago is now not necessary until/unless you get several magnitudes up in scale, and while the number of internet users has gone up, so has competition, and the proportion of services that gets successful to need scale up to several magnitudes beyond the old chokepoints at the time is tiny.