I'd rather bother with the expense of having a secondary headset because I feel it's safer to be in radio contact with ATC and other aircraft around you, than not to. Additionally, a look through the AIPs reveals that light signals aren't even provided at a number of aerodromes, and that system wouldn't be much use if I had an engine failure in the middle of the Irish Sea, for example. My view is that if the technology is available, I may as well take advantage of it (notice that I'm not saying to the exclusion of all other methods).
I'd also like a headset for my passenger to use.
Thanks for the reminder though!
AB