All joking aside, if you don't have at least a fundamental grasp of grappling you are doing yourself a dis-service. Coming from a judo background I'm fully aware of how capable even an untrained person is of taking another individual to the ground if they have no experience in any sort of grappling.
One day out of the blue my sensei said, "You can never say an aikidoist dosen't know how to fight because you never know what else they may have trained in." That line takes on new relavance for me every few years. Cross training in other arts is invaluable because no single style trains for everything and there's nothing worse that getting suprised with something you've never seen or never trained for.