Editors, languages, SQL databases, AI engines, whatever…
90% of the time it boils down to “it’s the one we’re most familair with, the one we’ve used before, the one we are used to.”
Sure, there are differences, but for most work (especially Clarion type work) those differences are minor. Most programs treat the SQL database as a storage engine, and frankly there are a whole host of databases that will do that job perfectly well.