"While S&W still cataloged the 38/44 revolvers (there were two the Heavy Duty/M20 and the Outdoorsman/M23) into the 1960's, the high-pressure ammo had long since been discontinued out of fear that it would be fired in an unsuitable revolver thus turning the 38/44's into nothing more than an exceptionally large and heavy .38 Special to anyone but a handloader."
Not so much.
Remington loaded .38-44 spec. ammunition into the late 1950s, possibly the early 1960s.
The primary reason the .38-44 faded as a cartridge was multi-fold:
1. The entire purpose for the cartridge, the lawlessness of the 1920s and 1930s, faded with World War II.
2. Only about 20,000 .38-44s were manufactured, meaning that ammunition sales were never going to be all that healthy.
3. .38-44 HD ammo was, comparatively, a lot more expensive than standard .38 Special ammo, so most people were inclined to go with that instead of the specialty ammo.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.