I doubt if England ever had very different instrumental lineups for dancing than Scotland. The point is that dance tunes were conceived for ensembles that had basses or harmonic potential, and when they were played by solo instruments the dancers would be filling in an accompaniment in their heads, just as they do now when hearing a well-known pop tune sung as a solo line.

Often if you haven't heard a tune with its original backing, it loses so much that you can't imagine why anybody would care about it. I don't listen to much pop music and never have, so when some kid starts singing a current hit on the bus I can't see anything in it. If I'd heard it in its original band arrangement I'd know why they were so enthusiastic about it. Most people's experience of traditional tunes is similar; they haven't experienced them played with a full band sound, and they sound just weedy as solo lines when you don't know where they came from. (Shetland fiddling is one genre where a solo melody instrument has usually been the norm, but it has often used scordatura tunings to add a quasi-drone, is often played by two fiddles in only partial unison, and it was designed to be played in tiny spaces where a solo melody has proportionately more impact).