Thought I would add my two cents here since I found myself thinking about this same topic recently.
To address mark1313's points above:
1. Completely agree. St. Louis is a small city which means there is a smaller pool of native hobbyists and providers. Fewer people = fewer possibilities.
2. Agree with this too. However, I know that a lot of well known ladies visit here on a regular basis and clean up. Ashley Taylor, Adriana Deville and Victoria Jolie all come to STL a few times a year just to name a few. A small provider pool means that there is a lot of demand for these ladies and they do book up quick when they visit.
3. Dunno here. Everyone has an opinion about the indy vs agency question. Personally I avoid agencies and prefer indys. It's true that there isn't any real established agency here in St. Louis. With the small community, I don't think a professional agency could base it itself here and do well. One thing I've noticed is that a lot of the best independent ladies started in agencies and moved on. I guess agencies are a good way for ladies who are thinking about becoming escorts to test the waters and see if it's right for them. Agencies = more providers.
4. Absolutely true that STL has it's no-fun-zones like many cities. However, maybe I am just out of the loop and ill-informed but I think things aren't as hot as they used to be. I could be wrong though. When you hear about the activity in the Indianapolis area, and now Ohio, it makes our neck of the woods seem relatively calm.
One factor too is that there is a low cost-of-living in this region, along with a lower average salary range that hobbyists will have to fool around with. St. Louis has a reputation of being "cheap" and I think this has something to do with it. 400/hr is something of a national average for rates. That sounds completely reasonable when I'm in Chicago, Las Vegas, or just about anywhere else. Here it seems kinda high.
One thing I've noticed too that I can't quite explain is that the ladies here tend to have more limited menus. That's a pretty broad generalization I know, but it seems to be the case.
What you have here then is a small city, that can be difficult to visit because of few direct flights, that has a small hobbyist pool, where guys aren't willing to pay what they will elsewhere. It's kind of a perfect storm that means STL is just not never going to be a major hobby town. However, I do love the exceptions (ladies) that prove the rule.