Great post, bearisgray!
Your mom's rules were my rules when I made all my own clothes, and occasionally clothes for others. I especially NEVER wasted fabric if I could help it....even if I had no idea what I was going to do with the scraps. That practice stood me in good stead when, for my son's wedding, I made four boys' vests out of 2 yards of woven-to-order tartan fabric for which I paid about $80 a yard!
When I first began quiltmaking I was not as careful, I think, about either the 1/4 inch seam or seam matching as I am now, mostly out of ignorance. Now, I'm a fanatic about seam matching and have mastered, more or less, the 1/4" seam. But I'm still intimidated by HSTs and points drive me crazy. Mastering this hobby is a process, I've discovered.
My own mother didn't sew but she was a perfectionist in everything else she did, including laundry and ironing (maybe because she worked in a laundry), and cleaning. Growing up under that kind of edict, one becomes, I think, either a perfectionist her/himself or rebels and goes the "whatever works" way....which is all right, too. I don't pass judgment, since everyone is entitled to their own rules, way of doing, and end result. And because, frankly, doing the "as well as one could" thing is a real pain sometimes!
And I agree about the jeans. I grew up when torn and faded clothes meant something other than Fashion Statement, and yes, the faded and torn need to be earned.