Tripods used to be a pretty good idea in many shooting situations since good sharpness could often not be achieved otherwise. That has changed fundamentally, so people who tell you that they "would never go without a tripod" simply aren't paying attention to changes in technology.
An excellent body/lens combination will give you 7-8 stops or more of stabilization these days. This means that you can theoretically shoot with a 50mm lens and exposure times of 2 seconds and more. That is indeed theoretical, but shooting at 1 second hand-held is not much of a challenge with such a body, and few people ever need that kind of slow shooting anyway.
Take an 800mm lens for comparison: 7 stops mean you can take sharp shots at 1/6s with an excellent IS system, and even a mediocre one with only 5 stops of IS lets you get away with 1/25s. Your shots are likely to suffer from subject movement long before they suffer from your body shake.
Tripods still make sense in two different scenarios: if you shoot with lenses too heavy to hand-hold, or if you decide you want to shoot with exposure times that are too long to hand-hold (say, several seconds) because you want to smooth out water movement or something like that. (Actually, MFT bodies feature computational modes that let you take such images with out a tripod, too, but Nikon does not offer that.)
My passion is bird shooting, and I make sure to buy only lenses I am able to hand-hold. I hardly ever use a tripod for that unless I sit in a hide or so. There is nothing to be gained by taking a tripod along on a walk, but it tends to get into the way quite quickly.
