It's up to each person, their planned activities, and other variables. I've been on multi-day trips with only a Leatherman, firewood was drug into the fire, I had a tent and a stove.
One time my buddy knocked my pack down a hill. I got it back, but all my gear was in the pack, I could have been left with not even a knife.
I like to keep some essentials on me at all times, and depending on the environment, I feel better with either a machete, large blade, or a hatchet.
I'd also be good to just have the BK-2 and a smaller knife. The BK-2 can chop, baton, pry, and make other tools, shelter, and cut through rabid lawnmowers. It's not an axe or machete, which have their place, but for backpacking it's a great all rounder.