Because of static electricity. Grounding coax shield plus resistor will cancel it.
Also antenna will be more quiet on RX than open one.
Mike
If I need to deal with static electricity a well placed shorted stub will be far better, and it may provide a slightly better match, not that a better match would be necessary in this case, nor would it be noticeable.
It would lower the resonant impedance (R on your antenna analyzer) of the antenna at the expense of added loss, and that loss would effect the antenna in both directions, lowering noise, yes, but also lowering transmitted and received signal strength as well. All that being said, 10,000 ohms in parallel with the 35 to 50 ohms that would be present in the antenna itself (horizontal to 45 degree angled radials), I don't believe any of this will be noticeable, including the change in noise level.
Would it not also put a limit on the antennas maximum transmitted power? The antenna as shown is effectively limited by the wire used, I'm guessing adding the resistor the power limit will be lowered to about 400 watts, but that is a guess... In any case, I highly doubt a single two watt 10,000 ohm resistor could handle the power some here in the states are known to use...
Another effect I see it having is SWR bandwidth, it would be wider as you are introducing losses, and losses increase bandwidth. How much is the question, likely not really much...
I guess I still don't see the point, but to each their own I guess.
The DB