That's still the case on intracity transit throughout most of Switzerland. Intercity trains are nearly always checked though. I think it's able to work because

That's still the case on intracity transit throughout most of Switzerland. Intercity trains are nearly always checked though. I think it's able to work because the fines are seen as high (90, 130, 160 CHF for the 1st, 2nd and 3rd violations and at some point they can force you to buy an annual pass) and because not paying the fines isn't really a viable option in Switzerland (they'll go into a debt register which is checked for a variety of reasons, it's kinda like the replacement for a credit report).