sweater theory

I'm new to knitting. Well, ok, I learned in eighth grade but didn't take to it and forgot how. I just re-learned last month. But I still consider myself new to knitting, since I never got beyond a two-inch-long scarf the first time.
I read a lot of knitting blogs, and I've read parts of a lot of knitting books, since they often have a bone or two for crocheters. Plus I've started going to knitting night once a week--even if I don't exactly feel like knitting, the knitters are so funny and great to be around, I really have a good time.
Well, in all these observations of knitting culture, what has really amazed me is how common it seems to be to spend all this time knitting with tiny needles, create a whole garment, and then discover it's unworkable and have to rip it all out. It's not just clueless folks; I watched this one incredible knitter rip out a whole small sweater at knitting night a few weeks ago. This girl is a very skilled knitter, I know she tried on the sweater as she was making it, and I know she checked her gauge, so huh?!?! And this really seems to be accepted as something to be expected with knitting, to my bafflement. I guess I'm a product knitter: if I'm knitting a sweater, sure it's nice to knit and all, but I want a damn sweater! A functional one! That is my purpose in knitting a sweater, and if I spend all that time on it and then have to undo it all, I'm going to be pissed!
Well, I started reading Sweater Design in Plain English and I got some insight into this situation that I'd like to share. Basically, because of the structure of knit fabric and how stretchy it is and how much give it has, there are a lot of ways to make a doomed sweater. By stitch:

• Garter - very elastic lengthwise, very expansive widthwise. A sweater in all garter stitch will get baggier and baggier in both directions every time it is worn.
  
• Stockinette - stretches lengthwise, becomes narrower widthwise. Stockinette will roll up unless it is edged with something else, and putting it in a sweater is no exception.
  
• Reverse Stockinette (make stockinette but sew it together inside out) - stretches widthwise, shrinks lengthwise, and doesn't want to go back to how it was.
  
• Stockinette turned sideways - stretches widthwise, shrinks lengthwise. In other words, the stockinette problems turned sideways.
  
• Seed stitch - reversible, stable. Also makes good trim for stockinette if knit with smaller needles.
  
• Ribbing - stretches lengthwise, very elastic widthwise. A whole sweater made of ribbing will show every lump and bulge and look horrible, in general, but ribbed cuffs and sweater bottoms are one way to make all that stretching stop on a sweater made in some other stitch.
  

Basically, it sounds like the only hope of having a sweater actually work is to have cuffs and a band at the bottom in something that wants to pull everything into the body (like ribbing or tight seed stitch), so that sweater kind of parks itself at those spots instead of hanging and stretching by its own weight.
Furthermore, the fiber can also cause sweater disaster, and not just if you pick something scratchy. Fibers such as silk, cotton, linen, and rayon -- the fibers that don't have scales -- don't attach to each other stitch by stitch like wool would, so fabric made out of these will stretch. Also, ribbing made out of these will not be as elastic as ribbing made out of wool. So if you're making a sweater out of one of these fibers and you want it to fit, you actually have to make it the size of the person's body or smaller!

Holy cow, no wonder so many sweaters end up in disaster. And before reading this, I would have thought that any commercially available pattern should be expected to work, but I bet a lot of designers aren't aware of all of these details. I'm nowhere near ready to design a pattern for knitting a sweater, but knowing all this stuff, at least maybe I'll be able to pick someone else's pattern and not end up having to undo it all.