Aye - different things come out during different stages of an interview process. Candidates find out positives and negatives throughout their discussions, just because a candidate is progressing through the rounds it doesn't necessarily mean that each interview is enhancing the firm/opportunity toe the candidate - I think you once mentioned that you'd worked in recruitment years ago, so I'm sure you've seen this first hand. Therefore it's important for potential employees to be given the time to make a fully informed and careful decision. Even if it works out well in the end, a rushed decision can never be described as careful.
As
@Basher says, it works for him/his firm, but both parties are likely to make more incorrect calls on each other if decisions are rushed.