A wise manufacturer makes what the largest number of end-line-users will buy, no matter how quirky those users’ reasons may be.
Folks being persnickety/perfectionist/absolutist about bullet jump, with Special ammo in Magnum chambers, will not simply go away. A manufacturer’s goal is to sell guns, and therefore earn money, from shooters on both sides of the bullet-jump issue.
Folks being persnickety, about the additional weight of a longer cylinder, will not simply go away, no matter how minor the actual difference.
Perfectionists may well be concerned about the ring of soot and debris that can accumulate, when Specials are fired in Magnum chambers.
If very hot Special ammo is fired, in Magnum chambers, erosion can, potentially, occur. If Magnums are subsequently fired, from such eroded chambers, the longer Magnum brass can fire-form into the eroded areas, making extraction difficult. I do not know how much firing it would take to cause a consequential amount of erosion, but this is a real issue.
Police departments, security entities, and such, can see Magnum ammo as a greater liability, and, therefore, not want to take the chance that Magnums might be loaded into their employees’ weapons. I do not know how many .38 Special revolvers are still sold to such organizations, but a large order is a large order, so, might as well be tooled-up for it. Then, there are individual-officer sales, to buyers who have to abide by employer policies. Retirees, who had, in the past, worked for such organizations, may want to buy a revolver exactly like the one they were issued.
Then, there is branding. This does not simply mean a manufacturer’s name. “.38” and “Special,” and “.38 Special,” are brands. Folks LOVE their brands. There are plenty of write-ups, on-line, and you-tube episodes, that can explain this, at length.
This is what comes to mind, with only one cup of coffee, thus far, this morning.