Quite a number of songs written by Burns were written to save pipe tunes which due to the times could so easily have disappeared forever. He also sometimes adapted local stories for the lyrics of the songs put to these.

That's not true. Burns got his tunes from published sources - he didn't need to write the tune down when sending a song to a publisher, he could just name it and the publisher could easily find it. I don't think there is any song in his entire output that used a Highland pipe tune - the pipe tunes he did use were Lowland ones also current as song airs or fiddle tunes.

He also didn't use rare tunes. He generally picked currently fashionable ones: it made sense to ride the wave when something like "Miss Admiral Gordon's Strathspey" was being played everywhere.