In the same vein, distributed DBs are not required for most companies (from a technical standpoint; data locality for things like GDPR is another story). You can vertically scale _a lot_ before you even get close to the limits of a modern RDBMS. Like hundreds of thousands of QPS.

I've personally ran MySQL in RDS on a mid-level instance, nowhere near close to maxing out RAM or IOPS, and it handled 120K QPS just fine. Notably, this was with a lot of UUIDv4 PKs.

I'd wager with intelligent schema design, good queries, and careful tuning, you could surpass 1 million QPS on a single instance.