You really need both fire and shelter to be a happy camper, but shelter can often be found or slightly modified with little or no use of a knife. Natural shelters are typically rock shelters or cave entrances, uprooted tree balls, tangles of debris, or whatever. My best nights in the outdoors have been in nice airy rock shelters, with good rain protection, superior ventilation, a soft sandy floor, and a scenic view - better than any tent or cabin!

Add a fire and you are set.....

Any well equipped individual will carry a blade of some sort, and the means to start a fire, but I have carried redundant fire starters for years. The need for fire is absolutely critical