This may be shocking to some, but the truth is, I rarely if ever carry a multitool when day hiking. When back packing I might carry one, depending on the trip and what other gear I have along, and how far back in the boonies I'm going. On the other hand, when sea-kayaking I always carry small but fairly complete repair kit, which includes a leatherman and a very small crescent wrench.

When deciding whether or not to carry tools, my approach is to look at what stuff I have, and try to imagine what tools I might need to keep that stuff functioning. It also depends on how remote I'm going, and how critical it might be to do field repairs. If I'm dayhiking, I usually don't have much gear with screws, bolts, or whatever, so why carry a screwdriver and pliers? I can manage most forseable jobs with a pocket knife. If backpacking, I might conceivably need to fix a stove or metal tent pole or something, so I might carry a leatherman. On the other hand, my sea kayak has some bolts etc on the rudder assembly, and I also have stoves, tents, etc, so a few tools might be necessary to effect a repair. Carrying a bit more weight is not such a big issue on my kayak. And I sometimes kayak places where it could be crucial to be able to do field repairs.

That's just my approach. I've been knocking around in the mountains and on the water for my whole life and it has worked for me so far (and I'm now past the Big Six Oh ). Others may have different approaches, and that's cool. Whatever works for you!