Does any one know why most quilts are made in "square", not octagonal or angled corners?.

Thank you, Lois

Short answer: I would say mostly cause the math is easier :lol:

Also it can be a lot harder to get equipment for graphing, cutting etc odd angles and that most quilts are made for beds that are a rectangular shape. Although I have seen some interesting shaped quilts, Star shape for a chrismas tree skirt and I have made a hexagonal quilt myself, but that was made with the english piecing method over papers, here is the link to it if you want to have a wee squise.
http://www.quiltingboard.com/posts/list/1328.page

For my good bed quilts, I round the corner. Not much - I can use a coffeecup to trace the curve in the corner. Then I bind with bias binding and I have a nice corner that will not get dog-eared.

I like your idea of rounded corners.