Unless I'm mistaken (I may be) GOG is primarily in the business of selling old games, which is why the publishers are willing to forgo DRM on the titles.
Publishers of new games (especially expensively developed new games) are more likely to fear a loss of revenue, especially in the crucial early period after release, without DRM.
Publishers of new games (especially expensively developed new games) are more likely to fear a loss of revenue, especially in the crucial early period after release, without DRM.