Yes, while running near my home I am usually only 3-5 miles from my car. So yes I make a descision to go with less because it is pretty pedestrian compared to other outings.
I have looked into other carry options and so far I find they move around too much unless they are small and have little room for extra gear. I have been looking at some fanny packs that hold either bottles or bladders but the ones that stay put while runnung have almost no extra capacity; mostly a small zippered pouch to hold keys and a pack of sports gel.
I agree that you need to adjust you gear to the endeavor but sometimes it is still limited by space and weight. If I am on an alpine style rock climb I may have a 10 mile approach each way so therefore I am far from my car but I still have to go quite light or it inhibits climbing; just what I can stuff in my Camelbak (Mule I think)so I am quite limited.
But all in all outside is outside and exposure can kill you on land and sea so the survival basics remain the pretty much the same. You still have to address the basic needs to stay warm, hydrated and getting rescued. In many cases (TWAWKI) any gear that addresses anything beyond this is extraneous. That does not mean it is worth having just that it is not necessary. The fishing part of some kits is an example.
In any situation you will need water; so having a water conatiner filled with anything other than water means you need to carry a second container with the water or you are not carrying any water at all
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. If you are in the wilderness you must have water so the obvious choice is to take water with you in a container and then refill in the field if need be. I rarely carry two Nalgene bottles at one time so for me the bottle kit has little value. My bottle is already filled with water.
I agree that the Nalgene bottles are great containers and have on occasion used them to keep somethng dry but normally I use them to contain liquids. I also agree that keeping a bottle based kit in a place like your trunk makes sense but as a kit you intend to carry it does not make sense to me.
As far as a car kit my car is very equpped but it does no good if I am not at my car.