@vreihen is right that in many instances insurance companies have been known to decline to pay claims when it is discovered that there is any code violation in the affected structure. This can certainly include failure to comply with NFPA-780 (the National Fire Protection Association lightning protection standard).
Lightning protection serves two purposes. First, it is intended to bleed off the static charge that builds up during a thunderstorm in hopes of the lightning strike finding some other target where the static charge is greater. Second, it is intended to provide a more attractive path to the Earth than the rest of your bulding provides . . . hopefully allowing the lightning to go to ground without cooking your building in the process.
There are very specific standards for lightning protection, including such things as minimum bend radius of the ground wires as they are routed down from the top of the building (this is because lightning has a tendency to take the shortest route and will arc from one point on the ground wire to another if the bends in the ground wire are too sharp . . . and, of course, that arc is a good way to start a fire in the materials in its path).
If I were to put a metal mast up above the top of my building, I would certainly provide it with a good ground wire, routed as directly as possible to a good ground rod.