
Valerie S. answered 06/14/19
Tutor of Many Trades
The Big 5, also known as the OCEAN or Five-Factor Model, as far as I can tell, was purposely designed as a clustering of common language terms used to describe personality. The way we tend to casually describe other's personalities is not typically neutral. So it is sort of a statistical summary of the way we already tend to describe our personalities.
This is not to say this is the correct way to go about things. For one, as its based upon statistics and not upon any psychological theories, nor is there any thing of a neuroscience nature to back any of it up. Personally, I see the biased way that the binaries are framed (high neuroticism=all bad, low neuroticism=all good) as one of the biggest problems with it.
But this model stays popular because it is among the most consistent and replicable personality models to come about. Consistency is not necessarily accuracy though. And is it worth it for a test to be consistent if it is simply a summary of our own social biases? These are all good questions to be asking.