One possible reason for dance tunes in Gm is that they were easier to play on F instruments, such as recorder.

The oldtimers must have been versatile. Looking at the first 15 tunes in Peter Barnes' English Country Dance Tunes, there are tunes in Bb, G, F, A, C, Ab and D. Some of these are the relative minors of the keys I just named.

I have the 1986 edition of this book, and it have given me much pleasure. There is a new edition which can be Googled and purchased by anyone who would like to do the same.pick up an instrument and play it, rather than get into arguments.