Quite a few of us find tango demos a wearying waste of good dance time. I've no doubt the various organisers know this, and may even sympathise, but they know that a good display brings people in, and this is reflected in the takings. I like to watch choreography, and I've enjoyed many great evenings at Sadlers Wells, but the technique and choreography I enjoy there are usually used creatively, and aren't just displays for the sake of display. I can't see anything much more than self-advertisement in most tango demos, and a dance that's little more than a technical display is just a bit too limited. I prefer the custom of the Cachirulo milonga in BsAs, where the regulars celebrate their birthdays and other events by dancing a tango with a partner of their choice, for everyone to watch. Of course, they are all excellent dancers, and everyone is likely to know them personally, or at least to have danced with them, as there's a feeling of family there, and the dances have heart. & of course it's a long night of dance, so it's no imposition to sit out for a while and watch.
The main reason for linking this video is that I've always enjoyed watching it. It's a choreography performed by technically brilliant dancers, but it feels fresh, while the agility in both high heels and polishing pads is both alarming and funny.