Missing something: The Appy League (and, AFAIK, the Pioneer League as well) is run differently than the rest of the minors. The teams are more or less non-profit small town deals, with community volunteers operating the whole deal without much expectation of profit. Bluefield is not guarenteed a team, nor is the Appy League guarenteed to have 10 teams. It could very well be that no major league team wants a rookie operation in Bluefield, and that some team will not use the slot for some other town. Towns come and go in the league all the time. You do not have to buy a franchise from an existing town, you just have to get a deal with a major league club to put a team in your town.
Reason: The Orioles have a team in the NY-P League, which is a "short season" league like the Appy and Pioneer, but which has more lax rookies-only restrictions of those leagues. It also has a team in the GCL , which is a "complex league", which is a deal where players play, with no crowd in attendance, at the spring training site.