You are right, in theory. But, I've been writing for years and I have had no luck getting things published anywhere until AC. Honestly, now that I've been writing for AC and Suite 101 for a bit, my confidence is better and, after the New Year, I plan on looking into other ways to get published.
It's not so easy for someone breaking into the freelance writing business to start making $200+ for an article right away. If it has been for you, then you are one of the lucky ones. Most people don't just walk into that.
I've always looked at AC as the first step in a process for me. I write to learn how to write better on AC and Suite. I think my writing has come a long way since I started. I admit, there are a lot of writers on AC who are not good writers and the pool is definitely not the best. But, there are serious writers there too, who are supplementing their income and learning as they go. As far as learning how to be a better writer, Suite actually is a much better site for that. But, between the two, I've come a long way.
I think anyone that is serious about being a writer wants to do what you are suggesting. Why wouldn't we? For some, AC is just right and they have no intentions of going elsewhere. But, for others, it is the foot in the door that we desperately needed and a chance to make a little money in the process.