[Carmack]

According to Cigar Adviser - Originating in Cuba, this was done to save shipping space. As a result, the process causes the cigars to burn longer and with a more consistent flavor, giving the smoker a more enjoyable smoke.

and Cuban Crafters say - What is box-pressed?
A cigar, while fresh and moist, is actually pressed in a wood box and the pressure creates a perfectly square shaped cigar. The box-pressed cigars usually burn long and give a more flavorful taste.