Hand sewing may not be common for large projects any longer, but it is still a vital skill for people who don't want to spend a great deal of money for alterations. Hand sewing is ideal for quick mending projects which don't necessarily require hauling out the sewing machine – to say nothing of putting it up again. And it's about the only way to sew on a button or reconstruct a worn out buttonhole -- in jeans, for instance.
Everyone should learn basic hand sewing. It's a great thing to know so you can hem your own slacks or mend a ripped seam in a shirt.