First, a neat image from Wikipedia
Here the cell tower has three vertical (or maybe slightly inclined to the inside) thicker pipes which are located at angles of a triangle and those three thicker pipes are interconnected with numerous thinner pipes and this yields a lattice tower with triangular horizontal cross-section.
Clearly you need at least three vertical pipes to make this happen. The design above with triangular cross-section is very popular.
However sometimes cell towers are built with square cross-section - they use four vertical pipes located at angles of a square instead of three pipes. It looks like waste of steel and design complication - what can a tower with square cross-section do what one with triangular cross-section cannot?
I could imagine there're was a difference when a tower had notable load concentrated in one direction. Yet I'm asking about cell towers that carry rather lightweight equipment and mostly have to withstand wind loads.
Why are square cross-section cell towers used instead of triangular cross-section towers?