Some voices just knock you down with their awesome power. A deep voice can make the walls rumble with its rumbly bass, and it's the ideal voice over tool if you're looking for power, confidence and authority.
Some classics are such for a reason. The weighty, booming quality of the deep voice has given life to anything from movie villains and master seducers to knowledgeable, affable, and relatable science communicators. With great power comes great responsibility, and it's up to you how to deploy the excellent qualities of this voice type.
There are many ways to get the most out of a deep voice. Narration is generally the most common, as there's something about the low end that has a hypnotic, authentic quality that instantly draws you into a story. If you've got a hero or a villain that you need to bring to life and imbue with an immediately powerful presence, you're golden (think the gravel-throated Geralt of Rivia in the Witcher series). Sometimes what you need is a strong, commanding tone that will instantly have your audience turning to their screens, whether it's a commercial or a movie trailer. The sky's the limit!
Aside from its rumbly quality, a deep voice tends to have a warm, almost husky tone that accentuates its natural boom. Some voices can feel intimidating (like James Earl Jones as Darth Vader), or others friendly, approachable, and practically avuncular (like Morgan Freeman in most of his roles). These voices can also have some rasp for that added grit as well.