Two reasons : ACID and single node scalability. Postgresql is production tested with terabytes of Ram and disk usage on a single node.

It has the jsonb column that can easily replicate the exact data model that you would use in leveldb.

However there's another significant reason - devops if you are looking to do anything serious with blockchain. There is really no good way to build a meaningful production application on the blockchain without serious devops because of leveldb. What is funny is that everyone who wants to do something on the blockchain first pulls the data into postgresql and then runs something on it.

Why have this problem in the first place? It just adds a few minutes to setup if you use postgresql instead of leveldb and get so so much more. And suddenly you can leverage all cloud hosted DB (rds, etc) and not have to focus on devops

What is this "devops" you're talking about?

It implements the SQL standard very well It includes support for "advanced" SQL stuff like window functions or common table expressions It is very innovative in terms of how plpgsql interacts with SQL It supports lots of advanced data types, such as (multi-dimensional) arrays, user-defined types, etc.

These are pretty good reasons :)

Which of those are relevant to implementing a blockchain node?