You knew it was coming, I have a gorilla in my logo for Pete’s sake.
Why deadlift? In all seriousness, the heavy deadlift is foundational to functional fitness. Working to increase capacity to, without the aid of assistance, lift something heavy off of the ground. Does it get more functional that that? The deadlift is equally foundational to build basic, whole body strength, that translates in every other facet of exercise. (If your response is, “not true, it doesn’t help my alternating dumbell curls” then you need to get in here immediately for further discussion of functional fitness).