I always feel the worst example of "but thats how..." is cabaceo at Milongas run by English people. The new dancers don't know about it and so either spend the evening sitting out confused or risk offending those who do by walking straight up and asking. It is very confusing as it varies from venue to venue. I personally can't keep a straight face ending up looking away in a fit of giggles, and so I dance exclusively with the unsubtle and the uninitiated. Also, what happens if one has a lazy eye?