Few words are more loaded than “should.” You can be sure there's a whole family drama behind it when someone says something like, “I should be a lawyer and not an artist.” And we make these kinds of statements.
“Now that I am past 65,” a friend said to me today, “I hope I can live a post-should life.”
A city can't live without shoulds. Walk on the left side of the road or on the right. Tip the waiter or no. Enter the tram in the middle or at the end. None of these are musts, exactly, but doing what you should certainly helps.
Still, just as it is better that your father or mother approach your childish mistakes with curiosity rather than with corporal punishment, it is better that a bike bell instead of a car horn move you to the proper place in the street.
Amsterdam has so many gentle shoulds of the bike bell kind, so many encouraging suggestions rather than harsh demands that you come to feel you can do what you want without irritating people too much.
The city helps you, in other words, live your post should life.