Now, who would invite during a cortina other than a beginner? Or someone who doesn't care what they'll be dancing to?
Someone who has a full dance card.
If I stay for, say, 21 tandas – consisting of, for the sake of argument, 14 tango tandas, 4 vals tandas, and 3 milonga tandas – then by the time my coat is off, my shoes are on, and I've walked to a table, the 4 vals and 3 milonga tandas are already promised in passing to people who like vals and milonga. It's more important to them that they get to dance
any valses or
any milongas than it is that they get to dance to some specific orquesta. Just about all of them also want a tango tanda at some point a bit later, too (they ask after the promised vals or milonga tanda), so that's 14 out of 21 tandas spoken for by 7 followers, leaving 7 tandas.
I generally hide out to change shirts and get water for at least 2 tandas, usually right after milonga tandas. That leave 5 tandas to cover everybody else. Most evenings, if I dance with only 12 people like this, I leave 2-3 friends prodding me to "reserve" tandas at the next event . . . meaning that I go into that event with stuff on my card when I arrive at the door. I left that out above to simplify the example.
Of course I try to wait for the favorite music of specific partners when I can, but often I have someone right in front of me waiting to be invited, and it simplifies things greatly to invite them while we can find each other, because milongas here are crowded and dim, and people are hard to find.
This isn't about "obligation." I like dancing with these people! However, each tanda not danced at all is a disappointment for someone . . . a greater disappointment than dancing to, say, Lomuto when they'd rather D'Arienzo. The followers I know find it more fun to face the challenge of an orquesta to which they don't often dance than to sit around not dancing at all.
I wouldn't consider this a "beginner" problem or a "not caring" problem, but a "having 10 years of tango friends in the same city, where there are far more followers than leaders" problem. Fortunately, said city has mostly competent DJs who don't play terrible tandas – and a significant portion of them display the upcoming tanda on a screen so that dancers can plan ahead during the previous tanda, never mind during the cortina. One also verbally announces. And quite a few have trademark cortinas that always precede specific orquestas, so if you've been here for a while, you know things like, "Ah,
Psycho Killer by the Talking Heads. We're in for some D'Arienzo."