Why do spokes cross under ?

OK, does anybody have any idea why spokes cross over and physically touch due to the deliberate threading of a spoke under the last spoke as it heads towards the rim ?
eg 3 cross passes clearly away from the first two crossings, but the final passes on the other side of the cross spoke.

I naively thought that avoiding contact with the other spokes would prevent a stress point where they touch each other.

Can anybody give reasoning why wheels are laced this way ?

Cheers Ray

Ray,

Its like weaving a basket sort of, the wheel ends up a little stiffer side to side but I am not sure that this has been proven scientifically, I think it is tradition based only.

Ed

I am interested in the different ride qualities of 3/2.5 ti vs 6/4 ti.

Thanks for your opinion