I went into the apple store in Basingstoke, UK the morning after the keynote. They had a Retina MBP out (only one, it is Basingstoke after all, and not for sale) for people to play with. They were taking orders for pickup in the next week or two.
Indeed. New Apple releases are events, and staff are paid to be able to get everything ready in time. It's not really feasible to do that every time some partner releases a new laptop that's not had any hype or media attention and no-one is going to be coming in the next day demanding to see it.
It's a luxury Apple have that other business models can't really afford to emulate.
Because the apple store only gets new machines once a year... so thats a bit of a loaded remark.