Any system with a limited amount of concepts is simple. Emergent properties are easy to predict and explore. Physics of "perfect friction-less sphere in vacuum" is so easy to understand we teach in grade schools and toddlers grasp it by instinct.
I can't (yet) reason about monoids easily. But I can reason about Git, even if I can't figure out the single command to change the state the way I want it and have to resort to multiple commands. I guess it's easier for me to think in graphs.