Same explanation as to why .44s use bullets from .425-.430". It started with the .44 S&W American which used the heel type bullets as described for the .38 caliber. The Russian government placed a large order for S&W revolvers but wanted the bullets seated into the case as is now standard. They reduced the bullet diameter to fit inside the lengthened case and thus the .44 Russian cartridge used a .43 caliber bullet. The .44 special and magnum evolved from the .44 Russian and thus it stuck.
Fortunately, S&W also reduced their bore diameters to match the new bullets, something Colt got around to only many years later. Old Colt revolvers in .38, .41 and .44 Colt caliber retained the oversize bores which required hollow based bullets to obtain even some pretense of accuracy.