Many home decor fabrics say dry clean only because they have a special coating on them of some kind or shrink when washed. If you prewash you take care of shrinkage problems, dye bleeding, and sometimes the special coating. Then I use them for projects. Sometimes the wrinkling, crunching etc. caused by washing adds to the texture. Depends on what you want.
For example, some satins get wrinkles that don't iron out, but it might be a look that you like for your project.
The home decor fabrics with a kind of rubbery backing is used by a friend to make quilts for the homeless. They are durable and sometimes waterproof, and very warm. She uses them for the backing of the quilt.