User blog comment:Willbachbakal/Singleplayer Weapons/@comment-3365911-20110409182324/@comment-1330314-20110409225258

It's because of the lore: Sophia Lamb had a Luger, while there never were any Colt 1911s in Rapture (as far as we know). Also, the latter gun has been way overused nowadays, especially in the Call of Duty series.