When would there only be one blind instead of two?

A. Imagine a full table where the players are numbered from 1 to 10. In this hand, Player 1 is the small blind and Player 2 is the big blind. During this hand, Player 2 leaves. On the subsequent hand, Player 1 would be the button, Player 2 the small blind, and Player 3 the big blind. However, Player 2 has left, therefore, there is just one blind: the big blind, Player 3.

In this same example, if Player 3 had left, instead of Player 2, there would be two blinds as normal: Player 2 would be the small blind and Player 4 would be the big blind.