I still wonder why Aerostich isn't making their own gloves. It's not like they don't have the talent.
Sewing leather takes different machines than sewing thinner textiles. And if you've never tried to sew glove fingers in reverse, tidy up the seams and then pull them so the outside is on the outside instead of the inside when you sewed them, I can tell you it's a process. Pros likely have equipment to do this. And it's still a hand done process, not a fast automated one.
So tool up to make leather gloves requires: Space, machines, special equipment and the talented people to operate them. I would be looking for someone in the US that manufactures gloves already and getting bids for gloves to my spec long before I'd be tooling up to make them myself if I was Aerostich, but that's a tough hunt too. Not every company that makes gloves is willing to, or has the capacity to, add a new, large line up of products spec'd differently than they already make.
Then there is the time issue. Approach vendor, get samples, share designs, get prototypes made, review/make changes, repeat until the product is what you want, place larger order, wait for delivery, if quality and time is acceptable, re-order, possibly in larger quantity, wait...
I'd love to have an Elkskin Competition Roper with hard knuckle armor. Not really willing to become a glove vendor though.
Here are a few companies that I wasn't familiar with for US made leather gloves:
Sullivan Glove They have a motorcycle line, but no knuckle pad/armor or retention except elastic.
Geier Glove Co The mostly make work gloves and some rodeo gloves, but show potential in the quality and seamless options, plus a snap roper and option to add a velcro strap, though nylon, not leather strap. Again, no knuckle guarding. They offer a wide variety of leather options though.
American Heritage/Bear Wallow Glove Co Only work/gardening gloves for made in USA options. A seamless version though, so possibly potential to make moto gloves. They do offer deerskin moto gloves, but they are not made in USA and only elastic retention w/o knuckle armor/padding.
Galeton Just work gloves, but some quality products and a pigskin offering with an adjustable retention strap that could be a starting point for a moto glove.
Midwest Glove A large mfg capable of wholesale production for other companies with a large line of existing products.
JRC Glove Co Some interesting variety of offerings and some moto, but no armor, but padded palm and lots of
style options. A little too proud of themselves for being the gloves worn by TV/Movie characters.