People don't instinctively have that need for variety, or tune sets for dancing wouldn't be such a rare phenomenon in human cultures.

For virtually all British 18th century dances that survive as written instructions, only one tune is indicated. The instructions synchronized the movements to the tune in the same way as in the present-day Hungarian dances I was describing. Probably the medley style went along with dances that didn't need instructions, but both types seem to have coexisted for a long time. The British didn't see variety as so all-important any more than anybody else did.

The RSCDS created an almighty muddle by reprinting dances intended for one specific tune and fitting entirely different tunes to them (the new tunes were either picked at random from old collections or else they were typically by Muriel Johnstone and typically forgettable). Often they used two tunes when the sources they drew on only had one. Someday somebody needs to go through their repertoire and re-edit it to reverse these weird decisions.