The vast majority of quilts I make do have either natural (unbleached) or bleached muslin as a backing fabric. I use it for quilts, wallhangings etc - you name it. It's a cost effect way to get your quilts completed (I buy it on large bolts) and it suits me just fine. On some occassions I will use quilting fabric for the back, but for me it's really far and few between. I do believe that there is probably a greater number of quilters who still engage in this practice than those that use "all quilting fabric" for the backing... but it just depends on your preference, overall design and ultimately budget. Some quilting fabrics are $9.99+ a yard and that's not always doable when you've already spent a small fortune on all the fabric for the quilt top. Sometimes - I'll even dye the muslin a specific color when needed and if practicable for my design. So I promise, there's nothing wrong with muslin! I like to get mine at Joann's when either it's on sale, or in between sales I'll use my coupons and it's great!
Explosive blessings, abundance and inspiration to you all!
- The Creative Seamstress