You'll find that a lot of cars used on the track or at shows have the plates removed or the registration covered & there are many reasons for it. Cloning (a car that looks written of or is likely to be off the road for a while is a bigger cloning target than one that's in regular use), speeding fines, congestion charges, track day prangs (though a better option is to remove or use show plates for the track time as this protects against cloning), location tracing of an immobile vehicle & its owner (steel a car that needs work but is in a less secure location & break into a house to get relevant documents).
For my Exige I have the plates on heavy duty velcro & rip them off for track time. For road use it's also useful so I can keep street legal plates on the car & still get the full front grill aperture (see attached image - my plate is mounted lower than shown with the top edge flush with the bottom of the grill) without having to replace front plates every 3-6 months when the lower edge has a tendency to catch on the top of speed cushions. With the velcro I can stop & retrieve the dislocated plate rather than replacing a shattered plate as well as getting the front clam repaired... again.
