I’d say the underlying roots of this phenomenon are twofold.
First, the two is actually not a “natural” beat to break on. All I mean by this is that, if you take a group of young children, without musical training, and ask them to clap on the two beat, they can’t – they’ll always clap on the one beat. Since many club dancers have little, if any, formal dance or music training, it makes sense to/for them to break on the one to the effect of 1, 2, cha, cha, cha. Aside from breaking on the 1 rather then the 2, this social/club version also tends to have all three “cha” steps evenly danced whereas a ballroom cha cha (and notice that it is usually referenced as such rather then as a cha cha cha) actually syncopates the two cha chas on the 4 and the &, with the 1 being a full beat for a very different overall rhythm then the club/street version.
Also, just as with the whole salsa/mambo thing, much contemporary music – as in what is being played in clubs vs. ballroom music – actually breaks on the one rather then the two. Add this to the aforementioned variables, and the fact that the majority of contemporary salsa dancers (numerically speaking everywhere but NY) break on 1 and I think you're well on the way to understanding the phenomenon.
Personally I’ve had everything from “I think you’re counting It wrong” (when dancing on 2) to “you know better then that” & then not taking a step until I switch to 2 (when dancing on 1).