I think there's a problem with the whole "survival kit" concept. It makes a lot of sense in some contexts, less in others.
Carrying a kit makes sense if you're just hopping in the car/jumping on the snowmobile/lifting off in the floatplane/ etc. and you might slide into the ditch/break a belt/make a forced landing/etc. and then have to get by until rescued. In this context, you wouldn't necessarily be carrying any gear, and all you would have is the kit, so you need a complete, self-contained survival kit.
Carrying an extensive, self-contained kit makes much less sense if you're backpacking/canoe tripping/etc., as you're already carrying everything you need to live in the wild. Being separated from your gear is usually a remote possibility, and real-world examples repeatedly show that in the worst-case scenario, people are able to get by with very little.
I do think it makes sense to carry a few light, compact items, regardless. A whistle, signal mirror, knife, firesteel, tinder, cord, duct tape, etc. take up very little space and weigh little. But some of those items are things you would use daily anyway, so this wouldn't necessarily be a self-contained "kit."