Giant pistols have very, very limited applications, especially with the development of first submachine guns and later short carbines. The only semi-practical use I can think of for the giant Dirty Harry-style monster is hunting/defense against large angry animals.

Otherwise, well, even before the advent of widespread body armor, pistols were very limited to the point where many troops have unhesitatingly just taken extra rifle ammunition to fill the space and weight that would have been taken by them instead. The only other niche role is as a backup/close weapon for someone who carries around something bulky (ie, a big launcher/machine gun or piece of heavy equipment). Except even there there have been better options. Especially since a big pistol would almost certainly require an exotic caliber that would be harder to resupply.

Of course, cheap thriller writers are infamous for just giving their characters the biggest guns possible. Before the Desert Eagle, Mack Bolan wielded an Automag and a .460 Weatherby rifle, something that Jerry “Detonics .45” Ahern took issue with.