There are many pros and cons other than just time-efficiency in a store.
Spatially, its actually quite complex to make one long line (it will probably have to snake around your store, and you'll need those awful movable tape barriers everywhere to make sure everyone keeps in line - customers hate these) and then to make one long line split evenly into several end points is not easy either (doing this may also take up a lot of valuable floor space).
Also, you could just have a store layout inherited from the 60s and its too expensive to change it right now...
Spatially, its actually quite complex to make one long line (it will probably have to snake around your store, and you'll need those awful movable tape barriers everywhere to make sure everyone keeps in line - customers hate these) and then to make one long line split evenly into several end points is not easy either (doing this may also take up a lot of valuable floor space).
Also, you could just have a store layout inherited from the 60s and its too expensive to change it right now...