With the right environment and correct gear, you can get by without a knife at all. Freeze dried food, aluminum poled tents, down or syn down sleeping bags, etc. However, I've always been taught that environments can change, gear, and supplies can get damaged or lost and survival depends on the tools attached to your body and your wits. Everything else is baggage.
Simple implements have helped me get home. I would never go into the woods without a decent knife attached to me, but that's just me.
The best tool we have out there is our brain. The tools are optional and can make it easier.