PostgresQL is an RDBMS and has increasingly been demonstrated as able to hold it's own against closed source rivals.
I think the OPs tossing NOSQL in there was poor form, and I think "SQL engines" could be replaced with DBAs. The world still needs RDBMS and we desperately need people who understand them from an engineering perspective.
But as an average app developer, I can scale my product to serve hundreds of thousands of people with really shitty DB architecture by simply throwing RAM at Postgres. That means Oracle corporate promises and hoards of query-optimizing DBAs are not the default for most fast (and even some moderately fast) moving startups anymore.
I think Oracle has a few features that postgres don't have.
Warning: conspiracy theories ahead - I have a suspicion that the biggest reason is so that their field agents (i.e. oracle-friendly DBAs : ) out in the field can always find some reason to choose Oracle over anything else.
Also: and this is based on once working with a Oracle shop and also listening to Microsoft guys: licenses fees can be a blessing in disguise, they aren't going to pay them anyways, their customers will and they will add 15%
Provide enterprise level support. That is, they provide 24x7 support with technicians who can troubleshoot problems with the database or provide basic indexing support, etc. They also will write specific patches for specific customers as needed.
It also has more features than PostgreSQL (more indexing options, custom SQL extensions, a better optimizer), is more stable, and has a lot more developers working full time on it.
PostgreSQL is good, no doubt, and GAFA have shown that you can take an open source DB and throw engineers at it to make it handle ridiculous scale. But what if you don't have those engineers to throw at the problem and constantly patch/update the DB? Finding people qualified is going to be both hard and expensive. An average MySQL DBA can easily fetch $200 an hour for routine work, and over $400 an hour for emergencies (my numbers are about 4 years old; it's probably gone up), and never be out of work or job offers. I don't imagine a good PostgreSQL admin is worth any less.
This is exactly what was said about IBM as IBM was being left behind by low cost replacements and competitors. Both IBM and Oracle have many of the same characteristics in terms of being aggressive with customers and influential in the C-suite. But that was not enough.
I think the OPs tossing NOSQL in there was poor form, and I think "SQL engines" could be replaced with DBAs. The world still needs RDBMS and we desperately need people who understand them from an engineering perspective.
But as an average app developer, I can scale my product to serve hundreds of thousands of people with really shitty DB architecture by simply throwing RAM at Postgres. That means Oracle corporate promises and hoards of query-optimizing DBAs are not the default for most fast (and even some moderately fast) moving startups anymore.