I am a novice about knitting when it comes to understanding all of it. Why are most sweater patterns from the bottom up. Why can't they all be...well with exceptions...top down, so much easier to fit as you go that way. I came from crocheting so this is why I am just wondering. Any thought on this would be fun to share and review. Thanks guys....I just got done making a very simple bottom up sweater and I thought for sure it was a perfect fit but alas it is a bit too small and my gauge was correct. drat.
I use both methods and usually knit in the round as I do not like sewing things up. I use 3 needle method for shoulders on bottom up items for stability.
The reason most knitting is made in pieces and sewn together is because it really came along after cloth clothing. Patterns for fabric are generally flat and the pieces sewn together. As many designers started here they then made knitted items the same. In design to have a flat pattern to measure your work against can be very helpful.
If you go back to historical crochet, Irish Crochet and the like, you will see they sew the motifs to flat pieces of fabric before joining together. This creates flat pieces to sew together.
Of course over time it has been changed by knitters and many now do things in the round. On a large object this can become heavy, which is why it may not be the most popular method but it all creates different forms and relieves boredom in my case.
The industrial revolution had much to do with changes as it was more economical to knit stockings and the like in one piece. All in all it comes down to preference.