I found it useful for a few things (on a m1 max so some differences).
In summer keeping the fans on at minimum speed keep the body of the macbook pro completely cool to the touch, while with the fans off it gets slightly warm and I found it unpleasant.
Also when running intensive applications (even some games) having the fans spin on at some speed (like 40%) will prevent the computer from reaching temps where the default would kick in at much higher speeds with loud noise. This way it stays quiet most of the time.