What I said is that they are a reward for a certain playstyle - map painting. You don't "happen" to hold enough lands to form an empire - you do because you're map painting.
I'm not saying that this playstyle is bad, but that's just how it is.
What you say is true, but you're wrong in the second half of your statement. Every time I've formed a kingdom as a duke, it's been incidental. Just as one example, when I started in Argyll, the only reason I formed Ireland was because I was taking territory from my brother, who kept trying to take Argyll, so he couldn't levy forces against me anymore. I snapped up counties he didn't have in order to rival his numbers, then waged bitter wars across several decades to finally absorb enough of his territory to vassalize him. Then, wouldn't you know it, I happened to have the dominion necessary to form Ireland!
This is how it always goes for me. I never set out to paint the map. I take territory either because I'm being proactive in my defense against a rival (strengthening myself while weakening them by taking counties), I want a specific region (usually for its defensible terrain, when my borders are on open ground), or because I've married into it. Therefore, when I acquire the lands to form a new title, I've done so incidentally.