13 isn’t the only popular unlucky number. In China, the number 4 sounds similar to the Chinese word for “death,” while the number 9 is bad luck in Japan because it sounds like the Japanese word for “torture.” Source
and then 4 + 9 = 13.
Similarly Japan and Korea also use a Chinese counting system and there are no fourth floors in any building.
there’s no 13th floor in casinos/hotels