Two counters:
1) An episode into Shogun World, I knew I didn't need to see another park after that. Or, rather, I didn't need to go on yet another make-believe adventure. Personally, I found the behind-the-scenes plot lines + the-park-is-going-to-hell plot lines far more interesting than most of the adventures that took place within the live, fully functioning parks. It was just really hard for me to get caught up in the stories/plights of the robots who hadn't yet been "awaken," and I feel like once we saw one story/adventure in those worlds, we saw them all. After Shogun World - and the taste we got of Raj World - I pretty much got the gist. IMO, like Jurassic Park, watching the failure and destruction of the park was infinitely more captivating than the functioning park itself. In other words, I just don't know how long they could have sustained a fully-functioning park and moved the story forward in a significant way.
2) All that said, why does everyone assume we're done with the parks? It's all but guaranteed that the show will find its way back to Westworld in some way, shape, or form - and along with it, probably another couple worlds we didn't get to see. We're either going to find ourselves caught up in some story that takes place in the remnants of those worlds - or - keeping with the Jurassic Park comparison, they'll go Jurassic World on us and re-open the park at some point, with bigger/better/"safer" features. Or we get both scenarios over the next couple of seasons. I'm just saying, I would be absolutely shocked if the show moves fully into the outside world at this point. I feel like this is simply an expansion of the story, not a completely new, irreversible course.