Originally Posted by
sir.pratt
probably because the 777 uses a completely new wing (as opposed to 74/76/73 series)
This doesn't quite explain then why the A330/340/380, with wing technology of the same era as the 777, do have winglets. And some versions of the 787 will have winglets (others will have a completely new style of wingtip).
I thought the folding 777 wings were only an idea in response to one particular issue, at Chicago O'Hare, where the main domestic gates were sized for the DC-10s for American and United which the 777 wouldn't fit. As widebodies of all types have pretty much disappeared from US domestic flights in more recent times, it is no longer a requirement.