I was taught, and tested on, takeoff and landing calculations. I have also had to work them out once or twice as part of the check-out process before renting various new types. But really I never bother with such matters in 'real life', for essentially the same reasons that MikeeB lists.
I do think that anyone contemplating landing or taking off from a new-to-them short and/or rough strip should do the calculations ... and triple check them ... and if possible speak to someone familiar with the strip. Best of all, eschew PA28s and other nosewheel airplanes (fine aircraft for touring, but not for this sort of thing: horses for courses).