I laugh when people talk about "breaking the design"
I am typing on a HP business notebook. The SD slot is flush with the body, right below the PCMCIA slot

Oh-so conspicuous it is
not
A memory card slot of whatever kind can have the slot flush on the body, or hidden by a cover. SD cards are slightly wider than a human thumb. Yes, a huge break in the design
How many people have sat there and said the SD card slot on their HP/Sony/Thinkpad/Asus/Toshiba/Dell/Acer/Samsung breaks the "design"?
How many people looking to buy would actually say that they refuse to buy because the memory card slot offends their preference for a clean design?
But an adaptor and cable sitting next to their system does not break the design
And Apple fan boys would be the first to congratulate Apple on joining 2002 the day they finally add a simple SD slot... if that day ever comes
New card formats come out all the time, and old card formats get obsolesced so quickly nowadays -- even SD has been superceded by SDHC, which means I have to toss out my external USB card readers I bought just a couple of years ago.
I assume that Apple only wants to devote precious port space to ports that will get used regularly during the entire lifetime of the laptop. Smart move on their part IMO.
You said it:
years. The trauma of having to get the wallet out and buy a new reader that is fabulously expensive at £10

Anyone with a reader circa 2005 will find SD/SDHC support
I use a USB reader. Its annoying because I have to remember to bring it with me when I travel (or bring the camera cable). I wish Apple could find a way to include one now that you can buy cards with enough memory to be used as backups or to hold several movies.
Sony's top of the range 11.1" ultra portable for years with each refresh have consistently included as standard a
multi-card reader, expresscard (used to be PCMCIA)
and an optical drive. It most definitely is nothing to do with size constraints