For me it is a matter of how often I need a survival-style knife. The answer is basically never, in an urban environment. I use smaller, multi-purpose swiss army knives or multi-tools instead.

So I have a semi-PSK that contains a mini-RSK. The point of the kit is to have a single package that I can throw into a small rucksack or large coat pocket without much thought. If it doesn't have a decent knife in it, I probably won't have a decent knife on me.