Unless you're already a name brand (e.g. the NYT, a handful of very high profile columnists, etc.) you can't just assume people will know the value of your work. You have to demonstrate it in some way. Providing half your content for free while keeping half behind a paywall seems like a perfectly reasonable strategy to address this discoverability problem.

I can't speak to the broader effectiveness of this strategy, but I know that I have paid to see some of a writer's paywalled work after first being exposed to their free content.