I have realised someone I travel with frequently dodges the full fare.
He basically buys the ticket using a railcard discount he's not entitled to. All barriers are automatic and I've never seen an inspector on one of these (local) trains.
His argument is the tickets are too expensive (which they are, £26 for a 30 min journey) and they get what they deserve.
I've been thinking about why I don't do it, and TBH it's probably more to do with the fear of getting caught (even though the risk is small), than any great moral virtue, but even so, I don't like what I've learned about him.