This is worth the read whether you have a subscription or not: https://archive.is/wXRzR Turns out the people who jump the turnstiles of subways are way more likely to commit violence or vandalism than paying riders. For years the Left said fare enforcement efforts were a waste of money, turns out they were wrong.
It would be interesting to know if the problems simply moved elsewhere. Why pay to vandalize when you can vandalize somewhere else for free?