Look at it this way, a bad scorecard is not one single instance of a mistake or incompetence, it's 12 independent opportunities. If you score a round wrong maybe you missed something, two rounds wrong and maybe you're having a bad night (incompetence), Canelo 114-114 vs Mayweather or 118-110 vs GGG and you're doing it on purpose (corruption)
Mainly corruption, funny how in 90% of occasions its the home fighter/a side who gets the generous scorecards.