Oracle licensing audits scare off plenty of folks.

At a small SaaS we were put off by the difficulty getting OracleDB's dev edition installed and working at all. While MySQL (then independent) and Pg were bare bones in comparison, they were very quick to get started, covered what was needed, and no risk of price spikes or time consuming audits. When pain points were encountered with MySQL and Pg there were plenty of flexible options to add into the mix.

Later I saw a competitor being crushed by licensing for Informix when they didn't need more than ~10% of its features.

Oracle DB may be excellent, but there is no chance I'd ever ever ever do business with Oracle due to their aggressive business practices.

Slightly off topic, but a friend of mine worked on Microsoft SQL Server a ~decade ago, and I recall all sorts of conversations on types of optimizations they were doing that sounded truly magical compared to other databases at the time. There was a meaningful frustration on the team that their features weren't getting as much hype as the databases du jour.

I think it's very relevant to consider that "enterprise" adjacent databases may not support the licensing you need at scale - but that doesn't mean they don't have great engineering and research teams that are solving really difficult challenges, and those challenges may be highly relevant to your workflows. Go into things with an open mind, if not an open wallet!

I do not think it is a mystery why people favor Postgres over OracleDB, is it?