[SmG Htgan]

Actually this began 200,000 years ago when the first pizzeria started packaging their pizzas for takeaways.
The pizzeria packaged pizzas in round boxes; The boxes were meticulously made from a square sheet of cardboard using a pair of scissors.
A competitor next door also offered the same takeaway option, and they infringed on the way the first pizzeria packaged their pizzas.
The owners took it to pizza court and the judge ruled that the competitor must not package pizzas in round boxes.
The competitor started packaging pizzas in square boxes, and business was bad. Customers thought that it made no sense to box round pizzas in square boxes and that the competitor's pizzeria was being stupid. Every customer who bought pizza from them asked "why do you box round pizzas in square boxes?" and the owner got tired of hearing the question.
It did not take long for this to drive the square box owner mad, so he went and shot the round box owner dead. But in order to spite all his customers he continued to box pizzas in square boxes. Being the only pizzeria offering takeaways, the customers had no other options but to accept the square boxes. The pizzeria opened up many shops all around town and eventually the square box became mainstream and nobody was questioning it any longer.

Or how about you use some common sense and realize square boxes are cheaper to produce and assemble?