IMHO the fact that we collect knives (and other weapons) is a part of primitive male behaviour, where we subcontious are drawn to certain objects that give us an edge to other men.
In the not so long ago past the best male got the best survival rate, the best female and the most offspring. Having the right tool to become the best male was important.
The fact that we evolved from using a sharpened stick to the H-bomb can all be traced back to this primitive response. Having a better hunting/defense tool made the difference. That's why these tools have evolved in such a way.
This behaviour is inherent to all males, although the amount of attraction toward these objects can differ.
Just like maternal instincts have a way more profound effect on females, knives, guns, survival equipment have a more profound effect on males.
This is not a bad instinct, untill a few hundred years ago these skills where needed to survive.
Now, unlike primitive female behaviour (taking care for infants) male primitive behaviour (war mongering/ survival skills) is been frowned upon by the society because primitive male behaviour is seen as troublesome in modern society.
Only in a true survival situation where we have to fall back on our own survival skills these objects become again important.
Once the whole public services are distorted ( say in case of a hurricane/war/famine) the male survival instinct is awakened and typical primitive male behaviour is regarded positive.
When everything is bought back to "normal" we have to supress these primitive reflexes.
I believe that we as knife collectors have a stronger then average primitive response to survival tools ( knives, axes, firearms, survival equipment).