Yesterday during the poker bloggers' tournament there was an all-in and call between two players who both had among the bigger stacks at the table. The dealer proceeded to count down the winner's chips, then count the loser's.
In the middle of this action, a player not involved suggested that it would be faster if the dealer just matched the stacks up against each other. The dealer politely declined to do so, but didn't explain himself.
This is a situation that comes up frequently, and surely there are many players--in fact, I would guess the great majority--who wonder exactly the same thing, but don't bother asking. So let me explain this little insider trade secret.
There are actually two reasons (well, I know of two; if there are others, please enlighten me in the comments) why matching stacks is not a good idea. First, once in a while in the process of doing so the stacks get jostled somehow and collapse, getting all intermingled, and it then becomes impossible to know how much each player had. It's a huge disaster, inevitably resulting in heated arguments, multiple conflicting opinions, the floor being called, security tapes reviewed, and the entire game grinding to a protracted halt while it gets sorted out. Nobody ends up happy. The correct procedure is for the dealer to count the winner's stack, then count out the same number of chips from the loser's stack, all the while keeping both sets of chips well away from each other, so that in the event of stacks toppling over, there is no danger of them getting mixed up.
Second, in some casinos they have in play chips that are many years old right alongside new ones. Chips gradually grind down from rubbing and bumping against each other, and they get thinner over the years. It then becomes very easy for a stack of, say, 20 chips that are mostly older, thinner ones to be the same height as a stack of 19 chips that consists mostly of new, full-thickness ones. Local casinos that come to mind where this is a real and ongoing problem include Caesars Palace, Imperial Palace, and the Golden Nugget. (For the same reason, you want to be careful when cashing out your chips in such rooms, because you can often easily fit 21 chips into one slot in the rack, and if the cashier isn't alert to the potential problem, you thereby shortchange yourself the value of one chip.)
When you're at a poker table where the dealers settle an all-in situation by matching stacks, you can be pretty sure it's a poker room in which management doesn't much care about the details of getting things right, and that attitude has been passed on to the dealers. Rooms that employ better-trained dealers and monitor them closely for correct procedures will not allow this time-saving but sloppy shortcut to be used.
So there you have it--one of the tiny mysteries of poker operations revealed.