In general "not wanting to understand, depend on, or work with other systems/teams" (often cause of dysfunctional eng/pm organizations) has, over 20years experience, been the number one reason devs (esp front end devs cause they tend to move the fastest (faster than traditional backend teams are prepared for) and have least experience in back end systems) go for something new, something they can control, something they can spin up fast and quick. NoSQL, cloud, anything they can do themselves.
The beauty of something like Postgres is that you don’t need to get your schema right on day 1. How could you anyways unless tou already know all future data access pattern?
I just need a ton of data, often redundant, that I never delete, that supports distributed writes and reads (ACID not required). The things I use Cassandra for would require huge Postgres servers and custom sharding/partitioning setups and Citus HA and all sorts of other things.
I will say, though, that it is important to get your schema correct at the beginning. I've also always worked full-stack, so I don't know what it's like not to have the ability to manipulate the database.