Whilst I'd agree with the generality that it can't establish, it's sometimes surprising. Ballroom also loses interest. I'm always surprised by the number of people from obscure and remote parts of Scotland, or from the other side of the country, who sometimes turn up at milongas - even in northern England. I think the most notable was the lady who needed a ferry to get across some loch in order to travel to get to a milonga - and a few hours by train to get to a metropolis. I also recollect the couple we met on a course who taught a small class in some obscure village.
However you're correct about 'establishing'. These are exceptions. AT required the metropolis of BsAs as its catalyst, although we shouldn't forget that
milonga campera.
@JournalInTime has already described this in Canada.