why does the owner of the building replace 13th floor as 12a or M?
The root of this practice is because some people are superstitious about the number 13 being unlucky, or they fear it (triskaidekaphobia). Owners know that they may lose customers that do care because of superstition. Polls have been conducted and show that individuals over the age of 65, women, and those with an annual income of less than $30,000 are more likely than others to ask for a new room if assigned to the 13th floor. Thus, owner of the building replace 13th floor as 12a or M. M is an obvious choice as it is the 13th letter in the alphabet.