I use muslin a lot. Something you may not know, a lot of the hand dyed fabrics are muslin. I dyes wonderfully. There is a lot of quality muslin

I use a premium muslin for ALL my quilt backs except for flannel for some kids ones.

What difference does it make what you put on the back if it never shows?

Muslin was my Mom's favorite backing. Just be sure it's good quality.....Everyone is right...it is so soft!

When I go to estate sales, I grab what muslin I can. I probably have 20 yards of scrap muslin. It's all washed and dried and ready for the next project.

I think muslin is used for backs and piecing a lot by quilters. I use the premium legacy from joanns, it is really soft washes up well. they have it in cream as well as white. I use it for my embroidery and small projects. I have quilts that it was used as a backing as well.

You are exactly right, you may use whatever you want. There are no rules, the notion that there are set rules for quilting (any part of the process) is just a myth.

Once upon a time everyone used muslin for backing. it was way before wide backing became popular. I use muslin and my walls don't seem to mind.

I use good quality muslin for all the backs of my small projects. Also made a pillowcase with good quality muslin and a large border remnant to adorn it, after many washes it is very soft and nice in use.

By all means, use muslin. I bought some Legacy muslin at Joanne's and it was better quality than some solids I've bought for 2x the price. Very little raveling.