I play Anglo and use all eight fingers, plus obviously my right thumb for the air button and sometimes my left thumb for part of a chord on pull. If I lost the use of either little finger I could still play, after a fashion, but my playing would be much changed. (A couple of years ago I had what was probably a small stroke, affecting my left hand and especially my left little finger. I gave up playing for the few weeks it took to recover.) I would expect it to be similar for all Anglo players, regardless of style, but I know little about what Irish players do.