Comment by immibis

Transactional databases are great, provided your write workload is low enough to fit on one server. If you have to scale up past that, you might have to use a different kind of database. But if transactions work for you, as they do for 99% of small-medium sites, they're amazing.

Multi-master transactional databases are an open area of research, as far as I'm aware, but read-only replication is a solved problem. Therefore your write traffic, including your transaction overhead, has to fit within one server's capacity, while your read traffic can scale horizontally as much as you like.