On several of my Kathryn Tickell CDs, the piano features as accompaniment on some of the tracks. It seems that when people were playing together in each other's homes, if the house had a piano, it would be used.

Also, dances were often held in village halls which would usually have a piano.

As someone said earlier, the piano is not very portable and its modern substitute, the electronic keyboard, which is reasonably portable, needs to be plugged in.