I suppose it is because the people are not poor, and as they are always able to pay the fare they do so.

They are too honest to cheat.

It is certainly a good way to encourage people to be honest, to put them on their honor and then rely on their own sense of uprightness.
The most curious sight I have ever seen was the Stock Exchange in New York.

It is used as a market for the purchase and sale of various articles, but there were no goods exposed for sale.

I saw a good many people running about talking, yelling and howling, and had I not been informed beforehand what to expect I should have thought that the men were getting ready, in their excitement, for a general all round fight.
However, I did not see any exchange of blows, and I did not hear that any blood was shed.
Another remarkable feature of the scene was that I did not see a single woman there; she was conspicuous by her absence.