I can tell you from personal experience what happens when your ski bases don't have a structure. Last year, the first day of the ski season, I was so busy with a new real life job, that I went skiing with the coat of storage wax on my skis (not even a scrape). It was a Maplus race base (purple), which is a relatively hard wax, and the conditions were a mixture of warm natural and man-made, with the man-made still in the form of machine-powder patches. Many times during the day, I came very close to going over the "handlebars." By the end of the day, there was still enough wax on my skis to scrape of. The idea that you don't need to scrape because it'll come of on the first run was completely debunked that day, under those conditions. It would've been a good Mythbusters episode for all the 17 people who'd manage not to fall asleep.
The purpose of the structure is to break the surface tension between the bases and the surface of the snow. Perfectly smooth, unstructured bases, will cling like glue to wet snow. Structure breaks up the surface tension.
There's a lot of science and art about what structure is optimal for what type of snow. For most non-pros, this is an overkill. I wax/tune my skis every weekend, and brush the wax out religiously (except the faithful incident mentioned in the first paragraph). I don't bother with my own structure tools, and the only time I do anything about the structure is when I get a base grind, but usually because of flatness or excessive repairs.
I'm of the school that a good structure on the bases is like fine wine. With regular waxing/scraping/brushing it matures and becomes faster. A freshly ground bases will take a few cycles of waxing/scraping/brushing/skiing to become slick again. I have hard time believing that FIS level skiers would actually regrind the bases for the spring portion of the WC circuit. Once you have a fast gliding base, don't mess with it.
I do most of my brushing with horse hair, nylon or bronze brushes. Steel brushes are very aggressive, and I'd recommend staying away from them, until you develop the confidence. It's very easy to over do it. Do not experiment on an expensive pair of skis.
Bottom line: brushing to expose the structure after waxing, is very important, or you significantly give up performance. Obsessing about the structure, unless you're a pro, is a waste of time.
Finally, regular waxing protects the bases against wear'n'tear. I have no proof of this, but my own experience, and experience of friends is that ski bases saturated with wax are more resilient to nicks and gouges. I have skis with 50+ days of skiing without a slightest nick in the bases. (Lawyer disclaimer: it's not Kryptonite - if you hit a rock, you'll leave some ptex behind, no two ways about it).