If you know what to look for you can always spot the controllers, so they are easy to avoid. not easy for foereigners of course, but honestly as tourist most public transport anywhere is confusing if you're not used to it.
That's my experience, at least.
When I was young and poor I "saved money" by buying the ticket in the morning, and only stamping it on the way back in the evening. I gambled successfully that if you get caught in the morning then you are the foreigner who does have a ticket (time of purchase is on the ticket) but "was not aware" that you had to stamp it.
And yea the "clueless tourist" approach works almost always.