That probably explains. 4-5 a year is rather high for one city in first place.
To be clear, that's in one
region: my city, another largish city 3 hours by road from here, and a few towns or smallish cities in the surrounding cantons. Not just my city.
We do have two or three large festivals annually which are open to everyone.
We have one big, general one (called Bailongo!). We used to have two others like that: one (Montréal Aime le Tango), where I volunteered, folded in 2016; the other (Festival International de Tango de Montréal) seems to have gone on indefinite hold in 2019. There are also several smaller ones with narrower themes: Festival International de Tango Queer MTL (queer tango), Festivalito Turco (Turkish tango), Tanguerafest (women in tango), etc. And now we have a "festival" surrounding the Tango BA (Mundial) qualifiers for Canada, though it remains to be seen if that will be every year, because other Canadian cities want to host that, too.
Reflects the mindset of organizers. May be the PYTs get recommended by the leaders who are chummy with organizers.
A few I know for sure are girlfriends, attending as +1s. The one time I
was invited to such a thing, I was told that it was role-balanced and that as they had a long waiting list of followers, I couldn't come with my +1. Seemed weird at the time, but maybe "emergency leaders" are a thing for encuentros with long waiting lists of followers (and vice versa). It was the "my +1 but not your +1 aspect" that seemed off, given that a few of the +1s were basically beginners while my partner was (and is) an experienced tanguera.