American sports fans, especially those unfamiliar with soccer, understand player acquisition as consisting of two processes: trading and the signing of free agents. When their favorite team needs to bolster its roster, they expect that trades will be made, or players will be signed (in the off season only); because player movement between clubs in the world's game doesn't follow this model, it can often be confusing to the average American.
The worldwide nature of soccer, and the high level on which it is played around the globe, means that competition for players is fierce. Because international boundaries, labor laws, contract laws, etc., all play a part in player movement between leagues and countries, the standard practice is to purchase a player, rather to trade for him. Trades occur, but rarely, and often with a fee included in the transaction. "Free agency", as it exists in the professional environment of the United States, only applies to footballers who are out of contract (i.e., a "free" transfer).
The purchasing of players hasn't been a major part of American sports for at least a half century; in the modern era, league rules are often at play when it comes to obtaining players, and these rules strictly regulate how, when, and if, a player can be moved from one team to another.
To further muddy the waters for Americans unfamiliar with the idiosyncrasies of world football, there remains yet another foreign concept: the loan. The idea that one team would loan one of its players to another for a indeterminate period of time has no parallel in our domestic sports. In fact, the concept is so foreign to some that they simply cannot fathom the reasons behind it; I've heard more than one talking-head or radio host rendered speechless (or incredulous) simply at the thought. For them, an athlete plays for one team and one team only; players deemed unworthy of the roster are either cut, traded, or demoted (minor leagues). For control of one team's player to be ceded to another ostensibly on the same tier of competition is apparently "un-American".
MLS chose to set itself up as strong centralized organization, in the mold of the modern-American sports league. The NFL, NBA, and Major League Baseball* all maintain strong grips on player movement within their leagues. Lack of any (serious) foreign competition for talent means that these leagues generally only import players; they're in little danger of losing their stars to clubs abroad. Without a powerful international body governing their sports, like FIFA does with soccer, the American "big three" control player movement in a way that serves their best interests while attempting to maintain competitive balance.** Because MLS sits near the bottom of its sport in terms of financial clout, it has maintained a de facto policy of only bringing foreign players in on free transfers; movement of players within the league occurs through the American practice of trading (although trading is not limited to player-for-player and can include other considerations like DP spots, allocation money, or draft picks). It would appear that this model serves two purposes: one, it allows for teams to upgrade their rosters and fill holes without extravagant spending, and two, it is familiar to the league's American fans.
MLS teams will eventually need to enter into the world of transfers, if only because it will reach a glass-ceiling of quality that cannot be broken through with the current policies. For those of us already in tune with the game and the way its business is conducted around the world, this will come as no shock. But for Americans whose world of sports has no parallels for transfers and loans, those concepts will continue to be just another reason to reject the game.
*I can't find anything that indicates that buying a player is specifically prohibited by MLB rules; that doesn't mean it isn't, just that I can't find any reference.
**Obviously none of that applies to the NFL, a league playing a sport that is played only (for practical purposes) by Americans.
A final thought for today that has nothing to do with the above post:
Just because you can write (about soccer or anything else), doesn't mean you should. Try to be sure you know how to properly use the English language in its written form before you go spewing nonsense and frustrating people (like me). An opinion alone is often not enough.
Sorry about that, just something I needed to get off of my chest; if it doesn't apply to you, please ignore it. If it does, please take it as constructive advice.
