It is very obvious why. The table is square and you have 4 corners on the table. Why would you need 5 or 6 legs to make the table balanced? Furthermore, on a round table, they will only add 4 legs in the middle of the table with a square support. There is no need to add more legs on a standard table. However, if you have an extremely long table it will need more support and they will add 2 to 6 extra legs on the table depending on how long the table is.