With a bad hand you would be tempted to just pass without a second's thought. If you happen to have a good hand, though, you need some time to think about what to bid. If you finally decide to pass, you will have (unlawfully) shown some values in your hand through the slowness of your pass. Now partner, depending on whether or not you made a slow or fast pass, may decide to take another bid.
This is why, in duplicate bridge, skip bid warnings are often used to tell one's opponents that a skip bid is about to be made. In every bidding box there is a red card that says Stop. To make a skip bid warning:
The next player must then wait for 10 seconds before making his call, even if he has a lousy hand and has nothing to think about. The 10 second wait is supposed to prevent the unlawful conveyance of information by requiring players to make all their bids after the same time delay.
99% of uncontested game auctions end with three passes, so no one expects you to pause here before passing.
Some examples of auctions where you are really expected to pause:
You are always expected to wait after a preempt.
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Similarly, you are always expected to pause after a weak skip bid by your RHO.