Years ago, my father brought home an entire dumpster load of good quality poly /cotton jacket fabric strips. Mom and I made about 200 shopping bags in various colored stripes of fabric, and sold them to benefit our church. These were unlined with no interfacing. 55 years later, my son complained that his 5 ("borrowed" from me) had just given out. If you need ones that stand, use interfacing. If not, don't bother.