triangles vs. I's

I was thinking about corrugation and kind of realizing that it is just like a set of triangles put next to each other and also lie on top of each other. the distribution of weight for a triangle is what makes it so efficient and so if you put a bunch of triangles together they would be even more strong since you are setting up three points in which weight can be distributed. cardboard is strong because of corrugation which is strong because of the triangular form it has inside and triangles are strong because they have three solid walls that place weight on two opposite ends of the bottom wall. however i was wondering why most construction companies use the I form beams to build building since they seem to be the least efficient beams, and i realized space plays a part in buildings. I beams you don't need many to sustain a lot of weight since we realized they hold the most weight. you just need a few distributed correctly and the space saved and the weight managed makes it somewhat more efficient to the building itself.