They were waiting to see if they lost. The projections were just that projections. They waited for certainty, and wisely so given the history of Gore driving to his concession speech and turning around. I was one of many people (I suspect) who advised the campaign that Florida was going to turn around and go Gore. I had an algebra spreadsheet and was working furiously, and predicted the turnaround as he was driving.
You don't concede when the facts are not yet in. They took that lesson from Al Gore!