Grounding eliminates potential that can build up on unbonded conductors/ariels.
During a very active thunderstorm, static activity along the highest and pointiest/corners/etc can be quite high. A direct strike will definitely result in burnouts/damage whether there is a ground or not. If the ground is inadequate it will just “smoke” just like a fuse and the excess kinetic energy finds it way, often with catastrophic consequences/destruction.
A completely ungrounded wooden post is the worst. Splinterville!
Insurance claims are a certainty with a direct dwelling strike due to the amount of damage.
Many electronics can be damaged permanently even with a strike to power lines miles away particularly if the wiring/grounding is poor. If there is no good path at the demarc and flashovers occur to conductors/feeders at points other than designed they are often huge and loud! Very destructive currents will be realized further downstream often far in excess of the capacity of surge protection. If you’ve heard a ‘pop’ noise inside your home when lightning flashes nearby you have witness this phenomenon. The standard flashover voltage is 6.6kV in an electric panel. This assumes the panel is properly installed and bonded of course. Even still, the 6.6kV has to be dealt with and most device power supplies have MOVs that can handle it. Of course they are limited by the number of times this happens.
I’ve seen improperly installed telephony equipment where so much kinetic energy was sent down 100 pair cables that every bend or twist in the cable had its outer jacket broken up or holed like a bullet was inside breaking out! Even worse, the wallboard was black with flame marks and copper plating from molten conductors. All of that happens in a flash literally. Definitely don’t want to be in the closet when that happens!