Why is it necessary to stitch the raw edges of a fabric?

When you make an apparel item or a home furnishing (made-up) product from fabrics, you need to sew the raw edges of the fabric (clothing item). There are a couple of reasons (including functional and decorative purposes) for sewing the raw edges of clothes and a garment. 

In this page, I have listed down some reasons behind sewing the raw edges of a fabric.

1. This is done to prevent the fraying of the yarns out from the clothes (fabric). If you remove the outer yarn of the fabric, you will see another yarn come out from the fabric after use of few times. The correct example is Saree. If you keep unstitched the two ends (in length) of the saree, yarns from the edges will come out. This is the reason pico stitch is done in saree edges.

2. This is done to give a clean finish (aesthetic purpose) to the edges of the clothes and garments. The loose and hanging yarns from the fabric (warp or weft yarn) may entangle with other objects when one wears it and may cause accidents. The loose threads (yarns) cause a discomfort to the wearer, and it looks bad as well.

3. This is done to secure the cloth edges of the fabric items and make the garment or other fabric-made items durable. To secure the garment edges, the edges (seam) are sewn after folding.

4. For some items like floor mats and fabric-made table covers, if the edges of the items are not stitched, and you continually use to cut the frayed out yarns to keep the edges clean, the dimension of the product will change after usages.

5. To make the fabric edge straight, the garment components with edges (ends) are stitched with a necessary seam type.

6. Sometimes to make decorative stitches at the edges of a cloth piece, stitching is done.