I use my most expensive knives for whatever tasks they are suited for.
My most expensive knives are kitchen knives. I use them to prepare food in the kitchen.
My most expensive non-kitchen knives are a couple of Zero Tolerance folders. I have used both of them for my normal cutting tasks.
I have a few traditional knives that I bought for collection purposes that I have no intention of using, though they weren't my most expensive. I have others similar to those that are user knives that would handle the same cutting tasks, so no need to mess up the collection pieces.
I get that some people are in the "I only buy what I will use and will use everything I buy" camp, but there are plenty of people who also buy to collect.
I was a member of a collector-oriented forum and in one of the threads about "what knife are you carrying today" there were a couple of posters who were literally shaking their heads saying "you mean you actually USE your knives?" Some of them had collections of hundreds of knives but had carried the same inexpensive folder for 20 years, and would not dream of ruining the value of one of their rare pieces by using it.
It's a big hobby, lots of ways to enjoy it.