Why? If you're financially secure and treat it like a hobby, why would you care? I don't track what my house is worth on a daily basis, so why would I worry about my funny books?
while this post is years and years old, the reason one cares is for insurance purposes...sure, folks don't track value of their house daily, but they do insure it, so they/you do have some approximate knowledge of value (or their agent does)...
until you face a theft, or fire, or some other catastrophe, you don't really realize that if your collection is not insured, it needs to be...regardless of whether you are financially secure or not...its the common sense thing to do