I'm seeing an increasing trend of pushback against this norm. An early example was David Crawshaw's one-process programming notes [1]. Running the database in the same process as the application server, using SQLite, is getting more popular with the rise of Litestream [2]. Earlier this year, I found the post "One machine can go pretty far if you build things properly" [3] quite refreshing.
Most of us can ignore FAANG-scale problems and keep right on using POSIX on a handful of machines.
But what about global customers? Most of the planet just eats the latency? What about single node failure? You usually need to scale past n=1 for a public facing service. It's not just about Google scale.
If your ui maintains state via some kind of async layer then the latency might not be observable at all.