Discretion went when electronic tickets became a thing.
With paper, no one knows if I've seen that ticket and, with just a cursory look, any ticket, depending on my mood, is valid for travel.
With electronic tickets, it's immediately flagged that the ticket is incorrect, and the machine is now prompting me for a response. This response is recorded and audited and, if it's not the correct response, I find a shiny 'Please explain...' note in my pigeon hole two or three days later.
So I have to write a report and file that, then await any further outcomes of that.....
So, with an electronic ticket, the easiest thing now for me to do is exactly what I'm trained to, regardless if it's a genuine mistake, you're a fare dodger or anything else. You all get treated the same because, if I don't, then I could end up losing my job.