Sorry msiemsen - just for the record, you're wrong.....

Corrugated soles ARE intended to reduce friction (and suction) on longer planes, especially useful when planing resinous woods.

Go look at the LN webpage for confirmation - they still offer this option on new planes.

It has nothing to do with flattening the sole of the plane.

I've used older Stanley No. 7s with and without corrugations, and the difference in "stiction" is VERY noticeable. In fact, if I came across a No. 7 in reasonable condition with the corrugated sole, I'd snap it up in an instant.