I am quite confused regarding an article in the Spring 2013 issue -Adding a Stretch Band to Stretch Fabrics. 
I am very new to sewing with knits and stretch fabrics.  There appears to be a disconnect between the stated purpose of the article of adding a stretch band for decorative impact, without compromising  flexibility, and the directions that add a band, edged with fusable tape,  which is then sewed on with a straight stitch and finished off with a foldover elastic. 
A straight stitch on a stretch garment?  Can someone give me specific examples of where this technique could be used ? Am I missing something? Looking forward to expanding my sewing knowledge.