I like to think of them as laws that can't be laws because they would be too strict for people to be punished over if they did not follow them. While it may be rude not to call an elderly man "uncle," it is not a criminal activity not to do so. This made it so this practice became an unspoken law through tradition and is considered customary in Singapore. Many of these customs and traditions have developed out of ideas of respectfulness and the thought that they are more logical. For example, having the slower people line up on the left makes sense so that anyone who needs to move quickly can pass them on the right. Another practical custom is to give up your seat on the train for the elderly, handicapped, pregnant women or young children. This is logical in a way, but is more so done as a sign of respect and kindness towards your fellow Singaporean!
The people of Singapore love cleanliness and order. It makes perfect sense for Singapore to have a set of unspoken laws and customs which help society be a bit more polite and orderly (like queues and neat lines!). Additionally, Singapore values unity because it is a community whose members come from many different racial and religious backgrounds. Politeness and respect are values reflected in Singaporean customs and traditions. Being kind to one's neighbor and fellow Singaporean helps in promoting the idea of unity under a common national identity.
