the mystery of primitives

i wanted to write a little essay on building optimisation in sl and i came to something very curious:

according to my knowledge of 3D and game design, you need 6 polygons(12 triangles) to make a cube. now iknow sl use a dynamic lod but its highest level is wasting tons of resource

i noticed sl use not 6 but 24 of them to dram a cube!!!! (each face is splited in 4, multiplying the number of faces by 4) (4times)

the same thing happend on prisms, 34 triangles instead of 8 (more than 4 times)

on cylinders, tubes and rings it seems even when NOT twisted, the primitive is divided in half in its length;
on cylinders, 144 triangles instead of 96 almost twice what is needed
on tube, 336 tri instad of 192
on rings, 288 instead of 144

could we have an explanation? it would mean that basically, most if not any sl builds eat twice more polygons as they should normally

client lag? look no further if peoples wear haircuts made of 92000 triangles (80 torii)

Lighting.

Lighting is calculated per vertex, so in the near view, surfaces of primitives are highly tessellated to prevent garish lighting artifacts (even flat surfaces). Also, reflection vectors and texture coordinates are per-vertex attributes, so tessellating surfaces ensures smooth(er) interpolation of these vectors across the surface of a primitive.

Also, curved surfaces (like that found in prim hair) always require many many triangles to prevent a blocky appearance.