They already installed contactless terminals in all stations
It's not going to improve payment, people who don't want to pay won't pay. The ROI on completely redoing turnstiles also probably wouldn't be great for the same reason. People hold the emergency door after all, and I don't see how a sliding gate can't just be kept open by shuffling in after someone else (the gate won't close with an obstruction right?)
I think you'd be surprised. Piracy went down when Netflix came along, because it made it easier to do "the right thing" (pay for your shit). I wouldn't underestimate the difference making it easier to pay for something has on revenue.
The gates in London do in fact close to prevent people from doing that. London doesn't have emergency doors like you have in NYC either, so that probably helps too.
Note that gate lines in London (and indeed elsewhere with the same system in the UK) will always have a staff member nearby to operate the gate line. If there isn't anybody available, the gate line is left open.
For example London Waterloo is an important enough station that for my last train home at 0105 from Waterloo, the last scheduled train from the station, the main gate line will still be running. There are likely a dozen or more employees still in the building, so why not.
But by the time it reaches the far smaller city where I live, its last stop for the night, about two hours later, the city is closed, nobody is attending the gate line, you could just walk out without a ticket.
The gates are however online, they just know there isn't anyone supervising so they don't close. Since I don't want to carry the paper ticket and dispose of it properly, I give it to the gate, which, despite being open, will conclude that this ticket isn't valid for any further journeys and swallow it. Attendants will take thousands of used tickets out and presumably they're recycled, or composted or burned, not my problem.
Also, in the event of an emergency you can force this style of gate, it will sound an alarm but an adult human is capable of exerting enough force to pass, which is what you should do if, somehow, you find yourself fleeing say, a fire, and the gate is closed but unattended.
I live in NY, that emergency door, alarm and all, will be propped open all day
Maybe if someone is watching people might be deterred but I've watched it stay open for 6 people straight with a cop standing 10 ft away, most of them don't care
It's not going to improve payment, people who don't want to pay won't pay. The ROI on completely redoing turnstiles also probably wouldn't be great for the same reason. People hold the emergency door after all, and I don't see how a sliding gate can't just be kept open by shuffling in after someone else (the gate won't close with an obstruction right?)