Hmm , i was working with the assumption you meant tangible results/benefits, seems i was incorrect and i retract my statement partially.
I will however die on the hill that not everything has immediate (or immediately noticeable to be more accurate) effects.
Learning to play an instrument doesn't always result in an immediate increase in ability, same with martial arts (the skill portion, not the physical/exercise portion).
If you limit yourself to only the things that have immediately noticeable effects then you are excluding potential paths for growth.