One probable reason is three of the last four attempts at remaking a classic spy series of the 1960s - Wild Wild West, The Avengers and I Spy - all sucked because the people who made the films had no clue as to what made the originals work.
The exception was the fourth, Get Smart, which managed to do it. I'm not counting the Mission Impossible films because they weren't anything related to the TV series, which is probably why they succeeded on their own merits.
They've talked about a Man from UNCLE movie for years, but I'm personally glad they haven't done it because they've have probably screwed it up. Until now - having a director like that and George Clooney as Napoleon Solo, now that may work. Clooney has the tongue-in-cheek attitude necessary for the part. Yet I can't see them deciding to make it an all-out comedy like, say, the remake of Starsky and Hutch.
The key will be who they get to play Kuryakin. Odds are he'll be reimagined as a female character, though. They seem to like doing that these days (ref. nuBSG, Hawaii Five-O...). Whatever they do, the chemistry needs to be there, otherwise it'll die on the vine.
And considering both Robert Vaughn and David McCallum are still very active - Robert in the US series Hustle, and David of course in NCIS - it would be a sin not to have them appear in cameos.
Alex
