[Boris]

In no limit, the decisions are more difficult when your action doesn't close the action.

so say you are the 2nd to act and there are 3 people in the pot. On the river, P1 checks. For whatever reason you decide to make a play at the pot and you make a big bluff. Now P3 has a marginal hand. He is much more likely to call if he knows P1 is going to fold. This is also somewhat true in higher limit hold'em games.

same concept on 4th street or the flop if the last person to act is on a draw and contemplating whether to call or maybe even raise.