Some fluids flow better in square pipes/fittings. Also, if the fitting is round, and the debris is square, it will clog easier. Very useful in cities with old water systems...
I just checked the price on a 1" broach, and they're $433 from Mcmaster. Ouch!!! Plus, I don't have a press big enough to fit a 24" tool. I think milling the square hole with an end mill would be the best. Perhaps it's not the quickest way, but it's cheapest for me.
