Someone writing the regs probably had OCD. But hey, militaries run on details...

We will now explain the way in which the cohorts described above pitch their tents. One tent occupies ten feet; this length is increased by two feet for the pitching, and it shelters eight men. A complete century has 80 soldiers, so there will be ten tents which will run in a line 120 feet long. Because the width of the hemistriga is 30 feet, 10 feet are assigned to the tents, 5 feet to the weapons and 9 feet to the pack animals. This makes 24 feet; twice this is 48 feet. So when two centuries camp opposite each other, a striga (strip) of 60 feet will be made; there remains 12 feet which will provide sufficient space for those coming and going. This space is calculated for a complete legionary century. Since 16 men from each century are on guard duty at any one time, they do not pitch more then eight tents per century. In this way their centurion has a place to pitch his tent on the same area as those tents would have been. Otherwise it would have been necessary to allocate more space.

Not sure if it was the romans exactly, but I read an article on why our railway line tracks have the width they do and it tracked it down to the width of roman roads - carriage axles for horse drawn carriages were made for road width, and it started from there.