Part of the difference is that there is a certain egotistical machismo in many Latino cultures (at least in that as I perceive it, it's very heavily emphasized that the man be "the man"), so I guess since salsa is the popular style of dance of the current day, that could have something to do with it. But otherwise, I do agree that the advanced salsero/as tend to dance only with those dancers in the clubs, and the rest of the beginning or insecure crowd tend to just stare and watch. It's not that I'm that intimidated, but I know I do more "ballroom salsa" and consequently I will ask people standing on the sidelines to dance, even if they don't know much. Probably if I started to take the intermediate salsa classes or start emulating more of the moves the salsa folks will do in many of the video clips you have pointed out (for which I am very grateful), maybe someone will notice and actually figure out I dance pretty decently, even if I don't do the multiple spin/hip bump thing. Of course, that sort of social casting will occur in any dance that I've gone to. It's just a question of how willing someone is to dance with me. If they only do one type of dance (swing or salsa or even just "ballroom"), they tend to refuse more often than if they were more broad in their dancing (do more than one club dance or integrate with ballroom).