Well because higher insurance premiums of course!
When I bought the 1968 Mercury Montego back in 2011 it was valued on the NADA guide for an "average" retail of around $7,500. So logically, that's what I sent the insurance value at.
It's now around $10,250, but was $10,787 last month. So I just jacked the insurance up to $11,000.
I guess claiming it as an "investment" to my wife is actually true, who knew!