Demand for anything in 10mm is low. I sell maybe 20 10mm’s a year out of the 8,000-10,000 guns we sell yearly.
Like the 500S&W, 224 Valkyrie, 375 H&H Magnum...it isn't a "for everybody" cartridge.
Compound that with the fact that the 10mm has no dedicated vehicle. I'd say for ALL that it has going against it, one random dude selling 20 in a year says a lot for a cartridge that has survived many cartridges that have been completely wiped from the Earth with less effort.
I'm kinda happy that HK hasn't made a 10mm. I'm pretty sure my checking account couldn't handle it.
To be fair, 10mm Auto's popularity was pretty short lived. Aside from the Bren 10 getting some airtime on Miami Vice and the round being adopted by the FBI in the late '80s/early '90s, it just has a cult following compared to the .45 ACP on one end, and 9mm Luger and .40 S&W on the other. .40 was born out of the fact that the FBI pud-loaded 10mm to reduce recoil in pistols, and S&W and Winchester developed a more compact round around the FBI spec 10mm loading.
That being said, HK for a time made MP5s in 10mm Auto and .40S&W, and Colt made a M1911/Mk IV Series 80 variant called the Delta Elite in 10mm from 1987-1999, then reintroduced it in about 2008 and still make a variant of it.
...and what resulted was a 30-year circle-jerk about the fallacy of service pistol "stopping power" only to end up back where they started.
Of course the problem with pistol rounds vs rifle rounds is that rifle rounds of smaller caliber can generate energy by increasing velocity to make up for diameter. Most rifle rounds are also tail-heavy spitzer/boat-tail bullets that tend to tumble and sometimes fragment in soft tissue. Pistol rounds can't count on that, so often times bigger is actually better.
Granted, if the FBI had issues back then with the stopping power of 9mm automatic pistols and .38 revolvers, why not re-adopt .45 ACP?