"Back in the day," we structured with sandpaper- roughing up the bases and creating drain paths for melt-water. Then came Riller- Bars, then came hand-stones. Shops used belt sanders, then moved to stone grinders- and sometimes computer controlled stone grinders. Advanced structuring is sort of the Marty McFly school of tuning: Back To The Future.
Yes, stone grinders have revolutionized tuning for MOST skiers, but for racers at the high-end, you'd better know how to hand-structure too. After all, your skis WILL sustain base damage over the course of the season, right? Perhaps even at a race... maybe even on race day? If you are going to repair bases on a short-notice basis, you ALSO want to restore/repair the structure, right? (The answers to all these questions is "true" by the way!)
To be prepared to deal with this eventuality, you might as well learn to hand-structure when there is no pressure. Hand Structuring is one of the techniques I am happy to show tuners in person... but online is just too risky.