Performances are judged on their looks.
I think the problem is to some extent that as soon as you start judging anything, you create a vicous circle where the standards that something is judged on becomes something that all performers are trying to emulate and/or exceed, and at the same time because all performers work towards these criteria the performances again educate the judges and inform the future standard, and it is very easy to slip into something that is almost a parody of the original intent because the judgement standards are fullfilled and exceeded by all competitioners, and subsequently adjusted, and exceeded again, and so on.
You can see that in almost all competetive disciplines - the specific ruleset and how things are judged the discipline will drift it over time to fulfill, and sometimes over-fulfill those criteria.
For me the "estilo mundial" is a fascinating example of that because we are watching it as it is evolving in response of who the first panel of judges were, and how the first winners were dancing. Over the last 10 years we have watched how competitioners changed their style to match the judging, became better at matching the expectations of the judges, and how by now everybody knows what kind of dancing wins championships, and i know people who started dancing tango by learning from teachers who teach towards championship dancing, and who only dance that style, and mostly when practicing for competition. I predict that over another 10 years we will see even more interesting developments as couples will on the one hand push the limits of what is allowed under the rules to distinguish themselves from the pack, and at the same time the "look and feel" of the championship style will become even more defined - and probably more extreme. Once we reach the point where the judges are ex-competitiors who have studied only competetive tango with the goal of winning competitions the circle will be closed, and "good tango" will be defined as "what wins competitions" which will be defined by the people who used to win competitions as "what we tried to do, only more so".
It is basically similar to the reaction that i have as sombody who likes to cook and eat to the more extreme variants of molecular gastronomy - i see what they are doing, i admire their skill and creativity, it is an interesting experience, but in the end i don't really understand pushing food as art far enough into the art direction that it is not really food anymore. And even the most ardent adherents of molecular cuisine don't actually live off foams...
Gssh