So like the programming books with a target audience of programmers this dance teachers assume you have a basic understanding and all you need is to learn this particular dance flavor or language of programming. This is a very inefficient way of learning and teaching.
Some people of course get programming immediately, they don't need to be taught it; same way some people get dancing immediately and need no actual teaching. But targeting that way of learning is inefficient; most people aren't born programmers or born dancers and have to struggle and plow through all of it on their own, repetition after repetition until they learn what the teacher is not teaching.
My particular peeve is on teachers that teach combinations strictly, as if all the dancer needs is a choreographer to lead and they just can follow. Now I had the fortune of a great dance teacher in college that allowed the fundamentals to evolve, and when she told me that a dancer can just look at a move and repeat it, I knew that professional dancing was not in the cards for me, no matter how much I may like to dance.
But aside from professional dancers, most people can't see a movement and replicate it. On the other hand once people have learned the moves they can string it together quite easily on their own, choreographer absent. You see this in every club where people taught themselves how to dance, and every time a dancer looses his place in time, is swallowed up by the immediacy and enters a state of flow. Positions move organically, naturally. So instead of giving the building blocks for this magic called dancing to occur, the dancer prescribes a set recipe where the dancers attempt to follow mechanically, not in the moment, not in the flow, but to an artificial count that in a club, that with a few drinks, in the intoxicating moment when you and your partner move in sync with it other matters as little as the skill of the valet parking attendant outside. It just doesn't come in to play. And play is what we want. Dancing is what we want.
Mechanical reproduction gets ingrained and eventually translated to dance, but that is the slow process of percolation (for me). Whereas doing moves while dancing needs no translating. You learn it directly to your body memory and get the pesky analytic brain out of the way.
Good dance teachers do both, the sequence for the people who need it and the basic building blocks (do a spin again and again until it feels right). Bad ones seem in possession of a demon called choreographer's ego and think only accomplished dancers can come up with dance moves.
The other corollary of this is the teaching of a weak lead on a beginner's class. People who don't know how to dance need a strong lead. A person learning to dance need to learn to lead strongly. Not with finesse. Finesse comes later, as you get better and better at dancing, you learn to signal turns, and movements with the minimum of effort, but at the beginning exaggeration, clear direction should rule the day. Make it clear. Then make it subtly invisible. Don't start with the mysterious, just cause it looks better or more proper. Damn competition dancing to hell, give me the practical, sweat-induced hormonal abandon that is pure dancing.