I'm not very sure about that ... music might have originated somewhere outside towns, but dance probably developed mostly in towns. It's just something that was danced in usual places where people dance socially, a kind of Cuban version of ballroom dance. Just this is social form of it (or presentation of how it was danced with some modern twist) and not competitive one
On salsaforums, people usually referred to salsa as street dance for some reason - though 99% of it was developed in dance studios ... so it's just another form of ballroom ... just like sensual bachata is other form of ballroom dance ... just not "international" or "american" ballroom
Formal and didactic training (inside studio walls) of social dances like salsa, zouk, bachata, Kizomba, AT, Lindy hop, WCS, etc
doesn’t make them another form of ballroom. (I have excluded sensual because it is a secular creation).
These social dances aren’t codified. Nor are they choreographed from social dancing perspective. They are primary social dances where any one of any skill level dance with each other. Competitions and performances are an after thought where only the ambitious try to participate. They make up less than 1% of 1%. You could go to these social dances without having taken a class too. Needless to say they are improvised.
Most of these dances are culturally associated and still have strong cultural affinity. Didactic training others not from within the cultural settings came about due to the popularity or demand.
You could argue waltz (a random example from ballroom) is similar. And make a case the same cultural origins can apply to origins of ballroom dances. There may be some place where more non-BR people dance waltz than BR dancers. Or are there waltz socials at the same level of popularity, frequency, and reach as the social dances(mentioned) where each has its own vibrant community?
A lot of people without formal training still dance salsa or semba or bachata at social gatherings, cultural festivities, and sometimes literally in the streets - makes them a street dance. Hip hop is also a street dance. That now it is taught in studios doesn’t make it a formal dance like ballet or contemporary. Formal and non-formal dances often borrow from each other. That’s part of evolution in dancing. It still doesn’t take away the line dividing formal dances for which you have to go to school and dedicate significant resources and informal ones. Same with the street dances. At one end you have waltz (culturally more of a relic now and primary a BR dance) and at the other end you have salsa or bachata which still preserve a strong cultural affiliation including a lot more non-trained dancers than trained. The number of studio trained salsa dancers pale in comparison to vernacular Latino dancers spread across carribeans, Latin America and North America. In between these two extremes of the spectrum is AT. A strong cultural affiliation, a social dance, not BR (though it gave rise to BR Tango), but even in Argentina, only those trained in it go to milongas. Unlike salsa with average Latino, an average Argentinian is unlikely to know how to dance tango. Most don’t. Viewed from its historical evolution AT can’t be called a street dance like salsa, bachata or hiphop (non partner dance form can be). Neither can it be called another form of Ballroom. I haven’t heard any AT dancers call it a street dance. It is considered social dance. While salsa is both a street dance and a social dance.
P.S. 99% of salsa was not developed in dance studios. Not even 50%.