Great question! I think the biggest deciding factor in a hubber's dreams for serial fiction revolve around the experience of the writer. In other words, how long has the writer been writing and how much does the writer know about getting published. I can't speak for anyone else, though, so this is my take on getting published....
I publish on Hubpages because it motivates me to write, which will make me a better writer. The more a writer writes, the better the writer gets! I know I must continue to improve if I ever want to find an agent. And right now, I'm writing a novel, so it gets published on HubPages as a serial hub. My dream is to entertain people with my writing, and I can do that on Hubpages today, right now.
I'm no professional writer, but I take writing seriously. I'm also very realistic about it. Until I improve enough to take publishing seriously, I will enjoy entertaining people while improving in my writing here on HubPages. Right now, I don't want to get my serial published, because I have to focus on improving as a writer and finishing what I start. That doesn't mean I won't consider it down the line, when getting published becomes a practical goal for me.