A large and expensive part of Toronto subway station design involves separation of paid-fare and unpaid zones. Wheelchair access is cumbersome, especially for older stations, as people must get on on elevator to get to the turnstile mezzanine, pass through a gate, and then gt on another elevator to get to the platform level.
in Wien, you just walk right in to the station, and down a single escalator to the platform. If you are in a wheelchair, you take a single elevator down. No turnstiles. No barriers. No gates. There's a vending machine to get your tickets, but nobody checks to see that you have one.
I don't know what the fare evasion rate is, but I like a system that assumes its customers are all honest.