You can pretend that it is not a big deal because "people have a choice for a 64 bit version," but the honest truth is that millions of consumers get the 32 bit version (on new 64 bit hardware mind you) because that is what came with their box and they don't know any better.
MS could have shortchanged that by doing the engineering necessary to pull off the feat Apple achieved with OSX by unifying the versions, or (lacking that talent, which might be the case) they could have been draconian with OEMs and forced any OEM that sold a 64bit capable machine to also sell a 64 bit Windows with it. They did neither, and we all suffer from MS incompetence on this issue.
Those people buying 32 bit Windows 7 today for their 64 bit capable boxes will be dragging down the market (especially the storage market) for years to come.