FP's Marc Lynch asks why we can't:
Good for the President's team to take the time to have a serious debate about this and not give in to the politically expedient path (in either direction). The readouts on yesterday's big Afghan strategy meeting reflect exactly what you want to see from a President making a tough call. I would urge them to set aside both of these corrosive, misleading notions -- that the choice is between "all in" or "getting out", and that the time for decision ins now. Why is this not the right time to muddle through, avoiding the worst outcomes and changing strategy at the local level where possible, while waiting for the political situation in Afghanistan to clarify? Muddling through might not make for sexy headlines, but it’s probably good enough for what the U.S. needs to accomplish in Afghanistan for now and is closer to the resources actually available.
Update: Goldfarb notes that Obama specifically derided "muddling through" during the campaign.