Why do we need to sew, anyways? Why not invent some sort of a glue (or a binding agent, to be more vague) to hold the pieces together? Something that'll last a 1000 washes and never wear.
Bonding agents are not the problem. The issue is working with cloth as it becomes a complex 3d shape. Picture adding pockets to a pant leg such that everything lines up to within 1cm. Now build it cheap enough to compete with someone making 250$ / month and working 80 hour weeks.
PS: Often a machine will cut the right shape and do the first seam, but after that it gets complex.
Patch pocket sewing has been automated for years.[1] For standard products like jeans, most of the operations are performed on an assembly line with special purpose machines. Direct labor content of the pair of jeans shown is 12 minutes and 15 seconds.[2] Even at $20/hr, that's only $4. Most of the human labor is putting parts into machines and taking them out.
We have one, invented thousands of years ago it involves cleverly inserting a string like solid binding agent repeatedly through the two pieces creating a flexible and strong bind.
But seriously, how many glues can you think of that are as flexible and durable as thread?
Some years ago, I actually had to learn about this. There are adhesives that are flexible, strong, hypoallergenic, and can survive laundering. They're used for disposable diapers, automotive applications, gloves, purses, luggage, and such. In a production environment they're applied as hot sprays, which requires compressed air and heated hoses and tanks.
Sewing isn't expensive, though. It costs more to get the fabric lined up properly for sewing (because that's manual) than to sew the seam.
(Former member, American Laundry and Dry-Cleaning Association.)
It would indeed be lucrative and I'm sure they have at least a group or two researching exactly that.
Thinking of it now my comment missed the availability of iron on seam tape which is used for water proofing but as I understand it isn't strong enough to bond pieces together without stitching.
Sustainability takes 3 aspects into consideration: Economical, Social, and Environmental. Inventing a glue and making the garment last 1000 washes makes sense environmentally, but think about the negative impact it has on the economies. Potentially, it will increase the unemployment related problems in many developing nations.
You would need to balance this sentiment with the fact that poor people wear clothing and would appreciate the cost savings with longer lasting garments.
I wouldn't wish employment in the garment industry on anyone, besides; we've already destroyed the local garment/craft economies in many impoverished countries by sending our old clothes to them for free.
PS: Often a machine will cut the right shape and do the first seam, but after that it gets complex.