There are several explanations as to why the number 13 is unknown:
1, Jesus was crucified on 13.
The thirteenth of thirteen people killed Jesus.
Because of taboos, westerners try their best to avoid contact with "13". In the Netherlands, it is difficult for people to find the house numbers of buildings 13 and 13. They replaced 13 with "12A". You can't find 13 rows and 13 seats in British theaters. The French are very clever, and there are generally walkways between rows 12 and 14 in the theater. In addition, people are also taboo to travel on 13, even more taboo to eat with 13 people, and even more unacceptable to 13 dishes.
Moreover, if the 13 of a month happens to be Friday, it is a very unlucky omen, which is called Black Friday.