We don’t really learn the reason, we just memorise the word for the number. Kinda like you know the word “dog” means a four legged cute creature, but not why the name is “dog”. The old rules are not something we are teached, I just got curious after a confused foreigner made me think about the system for a second :p
Try to throw the puzzle into sudoku.coach’s solver and you’ll find a ton of techniques that completely eliminate the guesswork.
I find sukdokus extremely fun and I never need to guess on a 6/7 out of 10 in difficulty. My suggestion is to take it slow at lower difficulties to get acquainted with the simpler techniques before springing to the harder difficulties.