Sure, it isn’t. But most things do not really need a distributed database, just something usable from multiple locations, and Postgres solves that problem easily.
Just because you, personally, don't have a good reason for using a distributed database doesn't mean there aren't folks who do!
Most vehicles don't need rocket propulsion, yet you can't go to the moon in an FSO Polonez ;)
We thought that, built an app on Postgres, got huge, now we wish there was a distributed Postgres vendor on AWS. I’m grumpy Azure bought Citus. Maybe Aurora is trustworthy now? Like 3 years ago I’d still hear about it eating peoples data.
City's is fully open source now.
Sure - but it'd be nice to have it managed for us.