I honestly don't know. I don't think there was ever a conscious effort to start using metaphors. "Hmmm. Let me now start using metaphors." (Kinda reminds one of Monty Python and the Holy Grail: "We are now no longer the Knights Who Say Ni.")
I do know that I've been more conscious of them (metaphors, not the Knights Who Say Ni - or don't) since writing has become a bigger part of my life. I'm aware of metaphors, I use them, and I think about how they affect my writing and my ability to convey my message.
So, sorry, Doug. I can't really tell you if it's natural or a learned thing. A bit of both, I suspect. How can we get there? By hanging on to outdated imperialist dogma which perpetuates the social and economic differences in our society! If there's EVER going to be any progress ...
(Sorry, had to let my inner geek peek through for a minute.)