If sewing is really a lost art, you kind of have to wonder who's been doing the searching-because it's not hard to find, if you do a little looking around.
Now, it's true that it's no longer the responsibility of the woman of the house to make all the clothing her family needs. That's all to the good, generally, since even a sewing machine only speeds up the process so much. But there are still people, both male and female, who make some of their own clothes at home. Their reasons vary from hard-to-fit figures to a preference for expensive fibers to a simple love of sewing, and they are out there; fabric stores couldn't survive on Halloween costumes and quilting supplies alone.
The mention of quilting brings up another question: what exactly counts as "sewing" in this discussion? If you only count it as sewing when someone makes a fully-lined, tailored jacket, then yes, sewing is in decline. On the other hand, if someone who sews fabric into a tube and adds an elastic waistband can be said to be sewing, there are probably more people who sew today than there have been in a long time. The rise of the crafty, DIY aesthetic has prompted a lot of people, especially young urban women, to take up such traditional tasks as knitting, embroidery and, yes, sewing. For example, patchwork quilting is huge; just do a search for "quilting blog" and you'll have more pages to check than you can get through in a day, and there are entire mail-order catalogs devoted to selling patterns, fabric, and accessories. People even make pillowcases and slipcovers for their furniture. What about putting on a new button or hemming a too-long pair of trousers? If those aren't sewing, what are they?
Perhaps the problem isn't the decline of sewing so much as the decline of traditional methods of teaching it. Young people these days are far more likely to learn from books, classes or online sources than they are from their mothers or grandmothers. Yet that can't be viewed as a disaster; the skills are being passed, even if in a nontraditional manner. We can lament the lack of little girls learning to sew dresses for their dollies at their grandmother's knee (assuming such things actually are falling out of favor), but that's no reason to mourn the loss of sewing as an art and craft. Sewing is alive and well, and will remain so as long as people need clothing and other textiles.