I make no attempt to keep up with such things, so, “not sure,” but my general perception is that new .38 revolver availability declined, for a long time, but certainly has been increasingly, lately. Shooters certainly do seem to burn through so much more 9mm ammo, so, no surprise, more 9mm ammo is manufactured. Mag dumps are trendy. Working on split times is trendy. Properly vetting an auto-pistol includes running a meaningful sample of duty/carry ammo though the weapon, to make sure it feeds the specific bullet profile, so, quite a bit of 9mm duty/carry ammo is sold, compared to premium .38 Special defensive carry ammo. There is, quite simply, economy of scale, when manufacturing 9mm ammo.
My sample of one is a late-era “baby boomer,” born in late 1961. After working as an LEO from 1984 to 2018, I initially kept carrying Glock and 1911 autos, after retirement, but, then, trended DA revolver, usually loaded with .38 Special ammo, for a few years, until 2024. Then, last year, arthritis caught up with my index fingers., prompting a shift back to single action and Glock triggers, so, 9mm is again my most-fired cartridge.
My sample of one is a late-era “baby boomer,” born in late 1961. After working as an LEO from 1984 to 2018, I initially kept carrying Glock and 1911 autos, after retirement, but, then, trended DA revolver, usually loaded with .38 Special ammo, for a few years, until 2024. Then, last year, arthritis caught up with my index fingers., prompting a shift back to single action and Glock triggers, so, 9mm is again my most-fired cartridge.