Have you ever considered the fact that, for one reason or another, some people may not be able to easily get to a store? How about the fact that some people like to save a few quid by ordering online? Some people even like to chance getting it early by ordering online in advance.
Contrary to what you think, people are not pre-ordering just to ensure they get a copy in case of shortages, because everybody knows that marketing trick doesn't work anymore. However, that doesn't stop people pre-ordering for obvious reasons I stated above.
Oh, and if you want to get clever and quote things from ads, I think you'll find that it is "
simplez"
for £25 inc 3day delivery from Hong Kong to Europe. Months before the European release and only cost me £5 more! 
