Because we keep on paying it.
My last 3 bodies have been grey, my last expensive canon lens was grey, anything else I've bought off brand or used.
Canon are taking the mickey.
The 40mm may well have been worth £229 to me, but it rankles a bit that it's worth only £129 to an american.
As much as I hoped for such a lens, I won't be buying it. Unless I get it grey.
If the retailers won't stick up for you (jacobs on sticky wicket, jessops indebited to tune of £10m to Canon) then stick up for yourself.