Well the thing is that the majority of people (I'm guessing) don't have HD sets in at least the UK, so having higher than standard definition wouldn't make a difference anyway as that resolution looks fine on CRT televisions. It's only once you've got an LCD or plasma television that it starts to look shit as the TV has to digitally upscale the image, very much like if you downloaded a small Windows Media Player movie and then tried to make it full screen (although TVs typically do it a bit better than that).
As far as I'm aware the CRT:LCD/Plasma ratio is very much in CRT's favour at the moment so while the latter is clearly the future, it'd be a huge financial waste to ship thousands of cables that'll never be used. We're talking millions of pounds/dollars/euros here.
I'm not saying it was necessarily a good thing to leave the £2-or-so cables out of each unit, but I am saying it's one aspect of cutting out stuff that might not be used (like the superior backwards compatibility) by a lot of people for reducing costs of each unit -- and that's an understandable strategy. Kind of comparable to Burger King giving every customer a 10p dip, even though many of them might not want or like it.
It's not a big deal to just pick up a cheap cable (avoid the official ones) for a few quid with the console; however, it should be made clear on the packaging or something that you need to do this if you want to enjoy true HD on your HD television.
Just as a side note, Microsoft did exactly the same thing with their core Xbox 360 configuration. It's no coincidence that the version with it included costs significantly more.