Holding and pass interference in football.
Personal fouls in basketball.
Totally subjective, totally selective, completely undetectable and EASILY RIGGED.
As a football bettor, if I offered you xx number of penalties in any number of games over a large enough sample, you'd consider that an edge.
Because it is.
Subtle, but an edge nonetheless - +EV
Referees all over the world have been caught over and over. It's not an open secret.
Years ago, I had a contact in the Netherlands who used to send me Euro soccer "steam" - games in the lower leagues that would MOVE BIGGLY for no apparent reason. I never asked 'why' but I knew...because 'we' made a killing!
MONEY = CORRUPTION = HUMAN NATURE 101.
Rather than sounding like a complete idiot demanding "proof" all the time, just assume that's how it is. Because that's how it's always been, and always will be.
Some of you are so naive it's unreal!