I believe there is a logical, and quite natural reason. I think it is the Ar15 syndrome. As we get older and older new shooters get younger and younger in comparison. What we grew up with from our fathers and role models is not what they grow up with, and becomes thier vision when they think of , rifle, shotgun, handgun.
We, in our late 50s and 60s, grew up with traditional rifles, lever actions in westerns and hunting, pump action shotguns, bolt action rifles, even semi autos with box magazines but all basically wood traditional stocks. Handguns were mostly revolvers, but when it was a pistol it was often a 1911 in 45. That's what saved so many of our fathers, and yes us, in 4 wars.
Its an evolution. They are growing up with fathers and role models using pistols almost exclusively, 9mm handguns being the vast majority, Glocks being the poster child. Revolvers are almost a curiosity to many, and 9mm is perceived as being THE choice handgun round. Its also why 10mm is being considered as a good alternative to large bore revolvers for dangerous big game. Pistols are the chit, and revolvers not as good in younger eyes.
Rifles are smaller caliber, defensive, plastic and steel, pistol gripped, and multi caliber, even in big gane calibers. . Even more shotguns are pistol gripped but traditional lives on in sporting shotguns.
That's what thier fathers, and role models use for everything, its what they learned in the military and law enforcement, thus they know and buy accordingly, and the gun companies are well aware. Thst helps push thier manufacturing options.
Of course this is a generality, there will always be those who buck the trend, and they are the future hope for cartridges and guns chambered in .45 acp and other calibers, plus revolvers in general.
Just an opinion.