By definition: sewing is the joining of two or more layers of fabric using needle and thread. For eons this meant hand sewing. Every stitch had to be carefully made, and the variety of stitches were amazing.
With the invention of the lock stitch sewing machine in 1846, this art and task quickly changed. Sewing production became faster, more accurate, and even more creative.
Yet, even after all the fancy modern conveniences of sewing machines, there remains the occasional hand work. Love or hate it. In either case, it important to learn the basics so you can do the hand stitching when required.
That does not mean, give up on your $15,000 high end wonder machine. Just keep in mind, machines really cannot do everything themselves.