I always have multiples. I have a small mini grip with deep carry clip that I use as a money clip and is inside my left pocket next to a LM micra. I usually also have a folder clipped to my RFP, and one clipped IWB, and many times one more if I'm wearing cargo shorts which is just about all the time.
I also always have a flashlight, CCW, spare mag, and a Bic lighter along with all my other 'pocketries'. Oh, and I have a disposable scalpel blade in the heavy foil wrapper they come in inside my wallet.
One knife is my all time favorite model which is a BM Rift forum model. Another is one that is screaming razor sharp that I don't use except to show someone a sharp knife or if I need something really sharp. The other is normally rotated and just what I'm liking at the moment and all are modern folders.
I usually move everything from one pair of pants to the next so I have everything. I had to go to court Tuesday so I threw my cargo shorts in my backpack and took out the bare necessities like my wallet, keys, phone, and some change for a parking meter. Even then I still ended up having to go thru the metal detector 3 times and they found 2 things with their wand . I had picked up a different flashlight because I was up early and strangely it's always dark if you get up early enough. I forgot about the small pill fob I carry my medicine in and missed some change. And I forgot about the folder that I clip to my underwear and sleep with. I changed it to the clean pair after taking a shower without even thinking about it. Good thing I didn't try to go in my normal cargo shorts.
A better question is probably who carries a knife 24/7. I do as mentioned above, I carry a folder clipped IWB to my underwear. I also carry a flashlight that gets much more use as I get up a few times almost every night and it's nice to not have to turn lights on that might wake someone and are blinding when half asleep. I imagine you will find many fewer people that constantly have a knife on them. I don't normally need it thru the night but it occasionally comes in handy after getting ready for bed or in the morning before I get dressed.