When you are talking about limits on velocity, such as black powder shooters are accustomed to, the mass of the bullet and its diameter are the only two things you can vary. To the minds of the 19th century riflemen, who were still shooting black powder well into the 1920s, 32 bore was a "small bore". Heck, the breach loader was newfangled to them. Smokeless powder? Pshaw! Only a passing fad. Just didn't make sense that a 30 bore could be effective against game animals.
Many serious target shooters of the late 1870s through 1890's preferred muzzle loaders in a 40 bore, and many of the target shooters using breach loading Ballards, Winchesters, Stevens, etc., still loaded their bullets down the tube from the muzzle. You would have a hard time convincing them that the 30 bore was better than, let alone as good as, the 32 bore.
Even so, the turn of the century 6mmPPC cartridge was the 32-40. You wanted to win a shooting match, you shot a 32-40. It was the accurate round to beat. The reputation for accuracy of the 32 bore had been around for several years at the time of the introduction of the 30 WCF. 30 bore didn't have that cachet.
Same holds true today. Tell a WW2 infantry veteran that the 223 round is better than the 30-06 and see his reaction. No matter the statistics, ballistics, and logistics, I warrant you will have a hard time convincing that old dude.
Sometimes you gotta look at the world through the eyes of old, hidebound, traditionalists.

They spend money too! --If you are selling rifles, you might do well to sell them what they want.
The phenomenon of hydrostatic shock even today sounds like hoo doo, when you consider the effect of a 45-70, a nice big fat heavy bullet with great momentum does have its merits in the arena of terminal performance. --You don't see professional guides in bear or buffalo or lion country carrying a 4000 fps 204 Ruger, now do you?
For the mindset of the time, going smaller than a 32 bore just didn't make sense to a lot of the old timers who fought in such places as Shiloh, with 58 caliber Minie balls, and for some I'm sure it was a bit of a stretch to accept a breach loading repeater.
Given the choice, I would probably choose the 32 over the 30. But then I guess I'm a hidebound traditionalist.