As somebody spending a large amount of my time working on postgres, and obviously being convinced PG is good: Of course people sometimes choose oracle on technical merits (I've not worked with modern sybase versions much, so I can't judge, although some sybase IQ numbers look interesting).

Golden Gate, RAC, Management Tools, stable plans, decent parallelism, decent partitioning, some columnar stuff - that's not just marketing fluff.

Oracle's politics / sales tactics, and cost are one large argument against, being able to influence feature development / add features yourself another, against Oracle, that I've seen driving companies - including big financial ones - away from oracle over time. Often that's not starting with the business critical stuff, but with some smaller project, and then grows over time.