Two tier strategy. Ordinary guards with machines. Enfocers with penalties. Same punter, different outcome. Because they can. Like the absurd parking fees in hospitals. We are fast becoming a tin pot third world shit hole.
Don't want to be unable to sit because 10 gits have chosen to sit in first class without a valid ticket. As they do. Every day. And the guard just wanders past smiling. I can't run the risk of standing owing to my back. And I'm 60 FFS. So I pay extra (discounted but only if I travel after 9)...
If you have broken the letter of their law they will do you. If they can generate a heartwarming headline out of it (are you pregnant, for example, or a bit doolally?) they may accomodate in return for a photo op. Useless money grubbing shitweasels, that they are.